This ISN'T a memory issue at all, but one of hard drive space.
Time for a clean up.
I'd use CCleaner
for starters and remove all of the junk files from your system. Then have a look at your installed programs and uninstall any you no longer use.
Once this is done, it's time to archive your data.
Music and pictures take up a lot of room, so best to burn them to CD for storage.