I finally took the plunge and installed Windows XP on my laptop; I could get by day-to-day on Vista but recently the little things (ridiculously long reboot time, inexplicable delays, excessive disk usage for no apparent reason) have been getting to me. Installing XP and getting it to dual boot with Vista is a well trodden path, but getting all the drivers doesn't appear to be, so here are my notes. I got everything working except the hotkeys (Fn-ESC to mute, Fn-F5 to change monitors etc). Bluetooth too, but that's never worked for me; I don't think the PSMC0A boxes have a Bluetooth module installed.
Step by step guide to installing XP on a system which already has Vista, and getting it to dual boot.
Once you've got this, now you need all the drivers. I had a second machine handy but if you're doing this on your only box, you'll want to boot back into Vista to do this.
Take care when getting drivers from Toshiba as there are two different M200 laptops. Mine is a Satellite M200, the Australasian model. In the USA the M200 is an older Tablet PC. The best driver source seems to be this folder full of .zip and .exe files at pc.toshiba-asia.com/support/doc/ [found via Allen Choong's blog]. The drivers you want start with SM200; you don't need them all, just the ones for your particular hardware. I got the ...For_PSMC0_PSMC1... ones.
THIS IS REALLY IMPORTANT: Install the appropriate SM200_XP_Intel_Chipset_Utility... one first, then the appropriate SM200_XP_TOSHIBA_Common_Modules... one, then the others. The hotkey utility and "toshiba utilities" installers won't work until you've installed the common modules. In my case neither would install even after I installed what looked like the right common modules installer, but this one seemed towork: common_modules_24589A.exe (v1.00.22SE) (which apparently is the version from a Toshiba A105-S2141). The hotkeys still wouldn't work after that but everything would install.
... more like this: [