The Indexing Service. Try turning that off.
No, you can figure this out by going to google.com and typing the following:
How to turn off XP indexing service?
Often when I am using my Gateway PC with Windows XP, either when I am using a program that requires little RAM such as typing in Word or when I click on a shortcut button to bring up a program, an unknown activity takes over the RAM and prevents me from continuing. I can hear the computer busily working away. This activity does not freeze the computer because I can still move the cursor but I cannot perform any action until the activity finishes, sometimes more than a minute or two. What could be causing this and how can I fix it? Thanks.