Oh dear, let's hope I can get this right! Most of this stuff is applicable to Vista too by the way, and there is scads of stuff about 64 bit on the MS website.

Win7 64 bit can address far greater amounts of memory in the PC. Think it's 128 gig instead of 4 gig. So if you have the memory, it's much quicker. Programs written for 64 bit are lots faster, but these are not yet the majority. Also, unbelievably, 64 bit Internet Explorer has apparently been deliberately slowed down by Microsoft so that it's not as good as 32 bit IE. I can't see much difference in practice but my internet connection is BT Stone Age anyway.

Security is better - there are features like Kernal Patch Protection which stop malware getting in to the Win7 kernel. Another security measure, years late, is that 64 bit Win7 has mandatory driver signing.

The downside of this is that any 32 bit driver will NOT work. In theory this stops you dead if you have an old printer, scanner, camera etc. However the only problem I have had is our printer (er, 11 years old!)now has to use an MS driver - there is no 64 bit Epson one. This cripples photo printing slightly as you can't download photo paper profiles etc. Realistically though the printer's on borrowed time anyway. I found a nice new Epson scanner driver online which admittedly cost me £8 but this includes improved scanning software so I'm OK with the cost.

Recent 32 bit programs should work OK - there is a 32 bit mode which Windows appears to take care of automatically. I haven't really had a problem yet with legacy programs, but it must be realised that some stuff may not work quite as expected. This may be nowt to do with 64 bit, just obsolescence! You can't expect, for instance, the 16 bit Desert Island screensaver written around 20 years ago, to work 15 years later (shame). In theory I could get most of Office 2000 to work, but since my new Dell has a preloaded starter version of Word, Excel etc on board it's not worth it. I'll probably cough up for Office 2010 eventually.

I suppose what I'm trying to say is go for 64 bit - it is the future. Dell didn't give me any option anyway! Meantime me little Medion netbook chugs away running XP and I intend to keep it that way until I go for an IPad (Pensioner Model).