960MB is boardliner, I'd generally say anything below 1GB (1024MB) then upgrade your RAM (you'll actually have 1GB installed but your video card will be using the the computer isn't reporting)
If your system is kept very clean and streamlined with the absolute minimum of crap installed and running in the back ground then it would be possible for it to run fine with 1GB installed, but start adding a few programs running in the background and you'll soon use all that and start needing virtual memory.
I'd suggest downloading the scanner from here and running it
http://www.crucial.co...emscanner/?click=true
Then consider either adding more RAM, or you may have to remove what you have already and replace the whole lot (this depending on how many slots for ram you have and how many are already occupied)