A 333Mhz, CAN be made to perform very well. the first thing is delete the programs you no longer use, via the Windows ADD/REMOVE programs. Keep using Scandisk and Disk Defragmenter to keep the system tuned-up.
the program you mention is common, and most likely can be had for free/shareware, check out tucows.com for similar shareware apps.
another good program is Disk Data, it gives an easy chart view of whos taking up the largest amount of data on the disk, so if ya want to delete it, you can.
be sure to clean out the temporary internet files, and the TEMP folder within C:\windows\Temp
that can store masive amounts of useless data, which was used when you installed apps. and were never removed for some odd reason.
the program you mentioned will clean dup files, by eliminating the backup Windows makes of some files. alot of programs when installed will make backup files, so if you installed 100 apps and each one made a backup, it will have hundreds of duplicate files stored on the HD.
do a search via START/FIND/FILES, and search for these files
*.LOG, *.OLD, *.BAK, *.000, *.001, *.002 *.---
delete em to the recycle bin, reboot computer, if everyhting goes fine, empty bin. if a file claims it need such n such file, see if it is in recycle bin, click RESTORE, to restore it.
after a day or so, with no error messages, empty the bin.
you can also do the same procedure with *.bmps, if you dont have a use for them. after finding em, look through em, delete if no longer want.
but if you want that progam, see if there is a demo, shareware version first.