Task Manager info
According to that page, if the peak Commit Charge approaches the limit, get more RAM.
From the screenshot you posted, that shows 128MB of RAM free. I'm guessing that this is not under your peak usage.
Pop a 256MB or 512MB stick in there, and your PC shouldn't have any low-memory problems for awhile.
Wow, just checked my Task Manager.
1GB total RAM
626 free
374MB of RAM taken up, with only 3 IE windows open - the rest is all my background apps I've got running. This is why I say that 256MB is the minimum nowadays; and I still see some systems shipping with WinXP and only 128MB of RAM. A fresh-installation will take up most of that by itself.:Q