^^ But then again BY the time Windows 7 is out; it wont be a pain in teh ass to upgrade RAM. Because Vista requirements have raised the bar so much that Windows 7; despite being a 3 year newer OS to vista; will be featherweight to the hardware.
And I do not think that a good antivirus + Firewall will take more than 100 MB RAM. I have 1 GB RAM and AVG Free + Comodo Firewall. And the AV takes around 20 MB ram during idle. The firewall manages at 10. And I doubt that it would increase to even a total of hundred while background scanning.
Also I have Opera 9.61 running with 7 tabs of the forum open in 1 window, 3 tabs of CNET.com in another window and bbc.co.uk 5 tabs in 3rd window. And the RAM usage is just 73.6 MB.
And Windows 7 is taking 485 out of 1 GB because there is FREE ram, its just utilising it while its Free. If programs ask for ram, there are a lot many un-essential parts of the OS that can be offloaded.