Um, all this talk about 32bit OSs not supporting over 3GB of Ram?
Here are the limits:
WinXP 32bit - 3.1 GB
Vista 32bit - 4.0 GB
WinXP 64bit - 128 GB
Vista 64bit - 128 GB (wait for it...)
Windows Server 2008 Datacenter - 2048 GB
That's lots of RAM. Oh and many of those are reduced by the Page-File, which can be disabled.
For the record, my Laptop is:
HP Pavillion dv1000
Intel Centrino - 1.86 GHz
1.49GB (1.5GB) DDR2 RAM
As long as Windows is managed properly, doesn't have stupid resource hogs (Norton, lol) and is kept defragged, it can run fine with ~512MB. Keep in mind that the RAM limit is almost inevitably going to be met by the motherboard limitations before the OS's.