Just fixed up my girls computer a bit she has something similar to what you’re referring to…
2.8ghz Celeron
256mb ram
5400rpm 80 gig
What helped the most aside from from the defrag/spyware etc. was turning off all the non-essential services that aren’t used anyhow, and getting rid of a couple useless things like timestamps and that damn legacy filename shit…
Oh yeah and save some time, setting prefetch on a couple commonly used programs…