I have been experiencing a lot of I/O activity which is slowing down computer.  CPU usage is also high.  Technician told me a file may be corrupt and that XP indexing function may be cause.  How can I verify this may be the problem and if so, how can I repair that file?--or any suggestions to look for other possible causes. Thanx, John

To check if the issue is the indexing function try the following:-
At the command prompt (Start/Run..) type "services.msc" and hit return.
In the window that opens up scroll to Indexing Service. Right-click and then click on Stop.
This will shut of the Indexing function. Close the window and see if the activity continues.

To fix a key corrupt file go again to the command prompt and type "sfc /scannow".
Make sure you have your xp install disk in the cd Rom.
When to hit return windows will check all your key system files for you.

Cheers

When I read the reply to this query I thought "Hooray! At last a way of speeding up my PC!" So I did what it said, but all that happened was that, after a long wait, I got this message:

Could not stop the Indexing Service on Local Computer.
Error 1053: The service did not respond to the start or control request in a timely fashion.

Any clues anyone, please?

If you have the Microsoft.NET framework 1.1 installed on your computer.
Here is the solution.
http://support.microsoft.com/kb/839174/

In services .msc right-click on indexing service and click on properties . Click on Startup Type Box and choose Disable. Close.  Reboot and Indexing service will not be on.

Many thanks, dlwolff0 and Snakeyes for your suggestions. I followed Snakeyes’ instructions, which seemed to work OK, though I’m unsure whether the improvement is significant.
I tried to follow dlwolff0’s instructions, but got a bit lost with determining whether I actually already have the required Service packs installed or not. I can’t spare the time just now for a thorough check, so am carrying on as I am for the time being.
I’m very grateful to you both for the information.

Try this free download from Microsoft. It provides an extraordinary amount of information regarding whats going on inside your PC and will help you get to the root of your issue.
Cheers
http://www.microsoft.com/technet/sysinternals/ProcessesAndThreads/ProcessExplorer.mspx

Many thanks for that! I don't have time to study it in detail just now, but will come back to it in due course. First reaction though, it looks very interesting and potentially useful, though the Help file didn't work, giving me a message that Navigation to the Web Page was canceled. I daresay I can work it out for myself, as it looks fairly intuitive. Thanks again!