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I haven't used an MS-Windows XP Embedded live CD, but I have used Linux live CDs. These are quite common and are intended to let you try out a distribution to see if you like it before actually installing it. Live CDs tend to be slow to boot, although this may be partially because the image also has to be decompressed. From the rattling and roaring that seems to come out of the CD drive during boot though, they aren't something I would trust to be mechanically reliable over the long run. I would also be concerned about dust collecting on the CD if it is left in the drive.
There are also versions of Linux distributions that boot from a USB flash drive (e.g. Mandriva, Ubuntu, etc.). That is something I would be more confident of than a CD. The concept though is the same - load an image off a read-only drive onto a RAM disk and run from there. I believe though that some of the USB flash versions also allow you to save some data files onto the same USB flash drive (the concept is that you can carry a bootable image and data files with you when you use a different PC). You could either create a customised boot image, or just add your application program to the data area of the flash drive. "Temp" files get written to RAM, so you don't wear out the flash.
People have taken the above concepts and copied them for MS Windows as well. HOWEVER, there are a few catches to this with MS Windows:
- You have to do some surgery to the MS-Windows image. Doing this for MS Windows isn't as common as it is with Linux, and it isn't officially supported. Some of your software may not work properly.
- There is a fair bit of work involved in researching and performing the modifications. This is enough to discourage most people from even trying it.
- Microsoft admits that people are doing it, but it isn't officially supported. That doesn't matter to a hobbyist who is doing it at home, but it can be a problem if you are delivering a project to a customer (i.e. you've "hacked" the software so the customer blames you for any MS Windows problems later).
- Updating the installation later (perhaps to fix a software problem) is pretty much out of the question. You have to create a "legitimate" image and go through the whole process of creating the "hacked" version again. This isn't what most customers would think they had signed up to if you told them they were getting Windows.
- There is a certain software toolkit available from some hobbyists (I won't name it) to help you hack the MS Windows image to prepare it, but Microsoft considers this to be a "piracy tool". They are more or less turning a blind eye to it at the moment because so few people are using it, but people are avoiding it because of it's questionable status.
- Distribution (delivery to the customer) of your "hacked" version is of dubious legality unless you have an OEM agreement for this directly with Microsoft.
If you're comfortable with the above, well then you might be able to put something together with MS Windows that does what you want. It's not something I would recommend though.
With regards to why MS Windows XP Embedded hasn't really "caught on" much, I think that is because it is really neither fish nor fowl. People wanting to use an ordinary desktop PC expect MS Windows XP to come already installed. The whole point of using MS Windows was supposed to be that you just bought the PC "as is". If you were going to install a different OS, then that removes a lot of the justification for using MS Windows in the first place.
On the other hand, for most people doing real embedded work, MS Windows XP Embedded isn't "embedded" enough. It's too big, too proprietary, too expensive, and it carries too much desktop baggage for their applications. Anything based on MS Windows Vista would be even more so.
The remaining market for "sort of embedded but not very" probably just isn't big enough to interest a company the size of Microsoft. They're interested in the consumer market so they can license their DRM (copy protection) systems for music and video to large entertainment companies. When they talk about "embedded", they mean consumer electronics, not industrial controls. The changes to MS Windows to produce the "Vista" version were primarily directed towards DRM and "media presentation". If you are "embedding" a system into a mass market consumer product to show pop music videos, Microsoft will be happy to talk to you about it. Things to make machines go "clunk - bang" though aren't what they had in mind.
There are also versions of Linux distributions that boot from a USB flash drive (e.g. Mandriva, Ubuntu, etc.). That is something I would be more confident of than a CD. The concept though is the same - load an image off a read-only drive onto a RAM disk and run from there. I believe though that some of the USB flash versions also allow you to save some data files onto the same USB flash drive (the concept is that you can carry a bootable image and data files with you when you use a different PC). You could either create a customised boot image, or just add your application program to the data area of the flash drive. "Temp" files get written to RAM, so you don't wear out the flash.
People have taken the above concepts and copied them for MS Windows as well. HOWEVER, there are a few catches to this with MS Windows:
- You have to do some surgery to the MS-Windows image. Doing this for MS Windows isn't as common as it is with Linux, and it isn't officially supported. Some of your software may not work properly.
- There is a fair bit of work involved in researching and performing the modifications. This is enough to discourage most people from even trying it.
- Microsoft admits that people are doing it, but it isn't officially supported. That doesn't matter to a hobbyist who is doing it at home, but it can be a problem if you are delivering a project to a customer (i.e. you've "hacked" the software so the customer blames you for any MS Windows problems later).
- Updating the installation later (perhaps to fix a software problem) is pretty much out of the question. You have to create a "legitimate" image and go through the whole process of creating the "hacked" version again. This isn't what most customers would think they had signed up to if you told them they were getting Windows.
- There is a certain software toolkit available from some hobbyists (I won't name it) to help you hack the MS Windows image to prepare it, but Microsoft considers this to be a "piracy tool". They are more or less turning a blind eye to it at the moment because so few people are using it, but people are avoiding it because of it's questionable status.
- Distribution (delivery to the customer) of your "hacked" version is of dubious legality unless you have an OEM agreement for this directly with Microsoft.
If you're comfortable with the above, well then you might be able to put something together with MS Windows that does what you want. It's not something I would recommend though.
With regards to why MS Windows XP Embedded hasn't really "caught on" much, I think that is because it is really neither fish nor fowl. People wanting to use an ordinary desktop PC expect MS Windows XP to come already installed. The whole point of using MS Windows was supposed to be that you just bought the PC "as is". If you were going to install a different OS, then that removes a lot of the justification for using MS Windows in the first place.
On the other hand, for most people doing real embedded work, MS Windows XP Embedded isn't "embedded" enough. It's too big, too proprietary, too expensive, and it carries too much desktop baggage for their applications. Anything based on MS Windows Vista would be even more so.
The remaining market for "sort of embedded but not very" probably just isn't big enough to interest a company the size of Microsoft. They're interested in the consumer market so they can license their DRM (copy protection) systems for music and video to large entertainment companies. When they talk about "embedded", they mean consumer electronics, not industrial controls. The changes to MS Windows to produce the "Vista" version were primarily directed towards DRM and "media presentation". If you are "embedding" a system into a mass market consumer product to show pop music videos, Microsoft will be happy to talk to you about it. Things to make machines go "clunk - bang" though aren't what they had in mind.
