About to jump to W7 from XP just 2 Question 2:
- I think 64 willbe the future, so any reason NOT to get it?
- I guess with older games, which I like, XP-Mode from the W7 Pro version comes is really important?
64-bit is the one to go for. If you have older hardware or devices they may not have 64-bit drivers available; however. You can use the Windows 7 Upgrade Advisor
to get an idea of whether drivers will be available. Vista drivers usually work on 7 if you can't get a proper driver, and many things will work fine with the generic drivers (monitors, mice, etc.)
As for XP Mode it actually isn't particularly suitable for gaming because it lacks 3D acceleration and does not support the 256 color display mode some early games require. These limitations can be partly solved by running XP Mode through VMware Player
(free), but even it doesn't have full 3D support yet. XP Mode is just a pre-installed virtual machine, not some magical compatibility layer; if you have a suitable XP license you can install that in a virtual machine manually to achieve the same result.
The majority of games will run just fine natively, of course, and those that don't will probably have some fan patch or other workaround. GOG releases will also generally work (even if not mentioned on the store page) except for a couple of rare cases mentioned elsewhere in this thread.