> Can anyone tell me which applications: can run on Windows XP; cannot run on Windows 7
Apart from all the old, dodgy and bespoke apps that don't get on with 7 (or which mess up with UAC in general), there's one big one for enterprises: the dreaded IE6.
Many poorly-coded intranet apps *still* don't work on any other browser, and because IE is welded into the OS, you can't (in an easy/supportable-for-IT way) run IE6 on Win7 or Vista. This lamentable technical decision, originally made to ensure MS's dominant position in the browser market, is now costing them sales. Whoops.
XP Mode would be the fix for this, except for the issues with Intel turning off VT on lower-end chips as an artificial product line differentiator, and rubbish OEMs like Sony turning it off because they're miserable idiots. Hopefully this will now stop.
[It remains unclear why the new version of VirtualPC, on which XP Mode is built, requires hardware virtualisation; the old versions didn't. VirtualBox's hardware virtualisation support is better now, and needed for running 64-bit guests, but for normal 32-bit XP there's no need for it.]