I found this topic after Googling exactly that: my computer freezes every few seconds.
It took me a day or two to figure it out, and all threads I've seen on the matter seem to have Norton AV in common.
My trouble started when I uninstalled Norton 360 to replace it with Kaspersky.
As it turns out - quite widely documented if you know where to look for it - a Norton (and some other AV programs too) uninstall may well corrupt TCP/IP and/or network connections with user set privileges.
To confirm this is the problem you need to to open the Event Viewer (administrative tools) and check if you get a lot of DCOM errors. If you do, you want to open one of these events and see what the text says (mostly cryptonic, of course).
In my case I found this: "Unable to start a DCOM Server: {73E709EA-5D93-4B2E-BBB0-99B7938DA9E4}", in this case the registry key was really the key to solving the problem.
Previously I had uninstalled LiveUpdate and some other Norton Services through the Control Panel, but soon found out they had not gone and kept running - obviously also generating warnings in the Event Viewer / Application window.
I thought I had the fix: downloaded the Norton removal tool from the Symantec website and cleaned out remaining Norton hooks, but... the problem was still there.
After copying the DCOM key into Google I found a whole bunch of references to corrupted WMI files, apps for which I had also seen warnings in Event Viewer.
I ended up doing a system restore, repaired the WMI Repository with these instructions (you need admin privileges...):
http://windowsxp.mvps.org/repairwmi.htm
and finally did a another uninstall of the remaining Norton files, put back in place by the roll back...
http://service1.symantec.com/Support/tsgeninfo.nsf/docid/2005033108162039?Open&docid=2006032009205413&nsf=sharedtech.nsf&view=docid&pid=2006032009205413&pkb=sharedtech
I just finished this, so, no guarantees but so far it works for me.
My suggestion is to NOT uninstall Norton from the control panel, but get the uninstall instructions/tools from Norton.
Given the number of pages dedicated to the topic, it must be quite a common little DRAMA.
Hope this helps someone.
Gerard
Edited to add:
As expected, my troubles were not quite over: you'd probably want to uninstall Norton com suis BEFORE repairing the WMI files.
In the end I restored the WMI's from a "slipstreamed" winstall directory on my C drive. You may of course also burn a slipstreamed CD if you prefer. See the instructions at the end of this web page:
http://windowsxp.mvps.org/repairwmi.htm