@Squarewave:
As promised, an update to say that I now have XP x32 running on my old Thinkpad using the IDE mSATA 2.5" adapter and Crucial M4 64GB mSATA drive. All working fine and fast. I see no reason why you should have a problem with the M2 version, or mSATA if you choose to go that way.
Just a few notes that may be helpful (I've learned a few things from the web during setup)...
- The installed size for XP x32 Pro, together with the collection of old Parallel port and other TE S/W comes in at 1.9GB. You really don't need a big SSD. As I think I mentioned previously, I've picked up all my mSATA SSDs cheap on ebay without a problem.
- I mentioned earlier that I thought XP SP2 supports SSD TRIM. I've installed SP3 and found that this still isn't the case, it's a bit too early to know anything about SSDs. In practice, it doesn't appear to matter. There isn't likely to be enough data flying about for the SSD to have difficulties with slowdown. If you want to do a manual TRIM (I think later windows versions do one about once a week), there are standalone utilities. Naraeon SSD tools is one, but I think there are others.
- Probably a more important one. For best endurance and performance, SSDs need to have their partition(s) 4k aligned. Later windows versions do this by default for SSDs, but the XP installer does not (something about using a 63 block offset rather than 64). To avoid this, it is easiest to create the primary partition on the SSD using a later version of Windows, and then have the XP installer install into the existing partition (you might be able to jump out to the command prompt on the installation CD and create the aligned partition that way but I didn't pursue it). Nareon will also tell you if your partition is correctly aligned or not. The first time I just used the XP installation CD and it complained, the second time I created the partition using W7 and all was fine.
- Again, for minimum wear, it is helpful to optimize a few things - disable the Page File (should be fine if you have 2GB RAM), turn off indexing (search is fast on an SSD anyway), turn off system restore, etc. Naraeon has an optimize function to do these and a couple of others in one hit but there is discussion on line.
- SSD-Z is also a useful standalone tool. It tells you basic SSD parameter data, partition alignment, SMART data etc. It doesn't have an option to initiate a manual TRIM though.
I hope this helps.