Windows xP cleanup (slow running)

Trying to improve performance of WinXP Home system running on a
900mHz, 128 Meg, 20 gig drive system.

The system runs slow and requires 35 seconds to open the FireFox
WebBrowser. The page file (virtual memory) is about 250 Megs.
Sometimes, I get a message the page file is too small.

The disk has been defragmented with good apparent results, however I'm
having trouble with the disk cleanup utility and not sure what can be
safely deleted.

The cleanup report indicates the following:

Downloaded Program files - 664KB
Temporary Internet files - 43K
Recycle Bin - 5076 KB
Setup Log Files - 1250 KB
Temporary Files - 37466 KB
WebClient/Publisher Temp Files - 36K
Compress Old Files - 2227 KB

Can I safely delete all these files to improve performance?

What else can be done to speed things up?

Thanks,

-Bill