My son continually bemoaned the speed of his ancient pc running XP on 3/4 mb of memory.
When mine caught fire after fitting a new video card, I gave him the 2mb memory which was now surplus to requirements. He used this to replace all his other bits'npieces of ram.
It now runs so much faster that he is no longer looking for a new computer!
You will notice the biggest difference when multi-tasking, either running more than one program or opening multiple windows in your browser.
Just doubled my old laptop ram from 256 to 512 kb and the difference is very noticeable. Faster and fewer lockups when the system temporarily runs out of memory.