Im using Win2K Professional 512mb memory.  Is there any way to determine what causes the system to lock up for 20-30 seconds at a time?  There appears to always be a lot of disk activity.  When I check system resources, it shows nothing of interest.   Is there any way to stop/reduce this problem.

Thanks
private

When you say you check system resources, does this mean you are looking at the task manager?
This should show you what process or program is tying up the cpu's time and causing the lock ups.
Also check the control panel\administrative tools\event viewer. This keeps a log of errors and information for the system, applications and security problems.
These two resources should give you a good idea of where the problems are coming from.

Yes, I have checked in BOTH places.  There is nothing in to indicate what is happening.  I know this is a common Windows, but I have never been able to get an explaination of what it is or how to prevent it.
private

This is not a common problem in XP with that amount of RAM. Have you checked your system for malwares lately?

There is a very good online scanner at http://www.trendmicro.com/spyware-scan/ Only run the online scanner, don't be tempted into other things

The first thing that came to mind, was a 5400 rpm HD w/ 4 MB of cache.
20/30 seconds sounds to me to be a bottleneck.
Hard Drives & memory are major players( potential bottlenecks ) in the performance chain w/ todays faster CPU's. Hope this helps

Unfortunately, the Windows task manager doesn't show all the processes that are running, and spyware can hide itself from windows. You need a program that shows all processes running. A good freeware program that I use is "Process Explorer". You can find it here:

http://www.sysinternals.com/Utilities/ProcessExplorer.html

There are also windows programs that can run in the background and cause this problem. With Process Explorer you can find them and then go to the program and turn off the feature that makes them run automatically.