A final, perhaps nooby, question about Windows 7 64-bit. Can it run 32-bit apps too or do you have to find the 64 bit versions?
It can run 32-bit apps. In fact, when you install 64-bit Windows you will see the directories "c:\Program Files" and "c:\Program Files (x86)" - the former holds the 64-bit apps the latter the 32-bit apps.
One issue with 64-bit Win 7 you must install 64-bit drivers. Fortunately I have been able to find 64-bit drivers for all the hardware I have (well, not for my 10 year old scanner ;)).
Another issue is that if you are running a 64-bit app that takes plugins, those plugins must also be 64-bit. For example, 64-bit Windows provides both a 32-bit and a 64-bit Internet Explorer - some plugins will work only with the 32-bit one. This is not a problem with Firefox as the only Firefox downloads for Windows (from the official Firefox web site) are all 32-bit, and most Firefox plugins are OS-independent.
Another issue - if you plan to run Eclipse you must install a 32-bit JDK - Eclipse will not run with a 64-bit JDK.