HD Space

Hi
My PC is 4 months old and my HD is 60GB. Today I was shocked to see that there was only 20GB left of free space. I went in to Add/remove programs and what is in there makes up to 5GB.
Also there is another couple of GBs of files /folders.
In the add/remove programs there are lots of WinXP updates, hotfixs (SP1) without indication of their size.
Does anybody know if this is what is eating my HD space?
Thanks
yiotie