Applications run Slow

[evilphantom]

We have a Mac OS 10.2.8 Server which worked until a recent Hard drive crash. Upon restoring to a new disk from and image everything got back to normal for about a week. Then programs started slow on the OS X server and file sharing had delays when users opened files [this is my biggest concern]. It can take up to 1 minute to open a file sometimes and as a result sometimes word will crash while opening these files. After the crash or stall the document can be opened quite quickly so the problem seems almost random. I believe the problem is associated with the fact that the OS is taking a long time to respond to the samba server or workgroup manager or whatever is trying to connect to it. I have replaced the hard drive twice and repaired permissions hundreds of times but I still cannot figure out what is wrong. Any Ideas?

OS 10.2.8 Server
G4 500 MHz
512 MB RAM

Thanks
Dez