i know this may sound odd but, maybe check your processes to ensure that you are not running any unwanted exe in the background. an example would be...daemon tool lite, adobe updaters. pull up task manager and check. if you are not for sure what is windows process or not follow these steps.
1) start
2) Run
3) (type) msconfig
4) Go to services Tab
5) at bottom check "hide all microsoft services" box. (this ensures you dont mess up what needs to be running)
6) remove unwanted
7) Go to startup tab and uncheck what is not needed.
I think your ram is fine. I curently run bad company 2 off of 1 gb ddr. which is half of the requirement. (about 750 available after windows)
the game runs very smooth for me with no hiccups.
I would check my page filing space if i were you just to be sure it isnt the ram. 1st PF should be about 1 1/2 times that of your max ram. yet i prefer to set it closer to the max physical.
hope it all works out for u
oh, and yea you should always prepare for a format. new viruses leak everyday, and systems crash. ccleaner has a restore tool built in. (awesome program!)
set the restore to a back up drive and youre good to go.