Hanging on startup (Preparing network connections)

I am running a Dell Dimension 4400 desktop with Windows XP (Service Pack 3). When I try to bot up, I get hung on the "preparing network connections" screen (before I can click on my user name). I can boot in Safe Mode (but not safe mode with networking) but after a second or two of the desktop showing up in safe mode Explorer shuts down. I can open Task Mgr but even if I open Explorer that way it shuts right back down. My internet connection is fine (as it's working on this laptop) and is using a Linksys-G wireless router and a cable modem. Before the last couple of days,computer has been running fine (albeit a little slow). My son noticed a burst of popups the other day (which has not recurred) and then I had one or two intermittent episodes of the "preparing network connections" thing. I downloaded and ran Trend Micro yesterday which found a handful of spyware/malware but nothing it flagged as a virus. Supposedly it cleaned them but today the hang at the "preparing network connections" screen has become an every time thing. I no longer have my Windows XP install disk (and have WAY too much stuff on this computer to lose anyway). [And I KNOW, I KNOW that i should have it backed up but, alas . . . ]

I spent about an hour and a half in bleeping computer chat but could not solve the problem, so I was sent here. PLEASE HELP!!!


Steve