Windows 7 Memory keeps draining

I have a Dell with 6GB of memory and Win7. Using the same software from my previous XP system, I noticed that every few hours of using my system I have to reboot cause the system says my memory is low.

Strange as I hardly am running any software. Cannot even access my e-mail using Outlook, then I reboot and all is well for another few hours.

So I modified some of the entries in MSCONFIG and it has helped, but with 6GB I should not have to do this. That is a lot of memory for what I am doing. Used to do the same thing on a 1GB XP machine and NEVER had any issues.

I have run all sorts of anti virus software - nothing. Should I be running them in safe mode?

Any help please would be most appreciated.

I looked at TaskManager screen and the FREE memory slowly keeps going down over a period of time without me doing anything. Available memory seem to be high but does not seem to make any difference.

Help.