I don't think that you actually want to format your drive as that will lose everything on it. This will stop your computer working at all!
Second I am not sure what you mean by: "my memory is almost full and I cant load many programs quick enough or sometimes not at all". It sounds as though you may not have enough memory (which is nothing to do with your disk drive.) If you have Windows XP you need at least 512MByres of RAM (Memory) or you will experience the symptoms that your describe.
The other thing that you should do is use the remove programs utility to get rid of programs that you no longer use and finally defragment your Hard Disk.
t
June 2008