If you find that disconnecting from the net or have any other indication that it's a trojan, ZoneAlarm will detect any outgoing port connections and give you the opportunity to stop it. It can mess with your high speed connection connectivity though, so after you use it and test a few times, you may want to disable it on start up (and it's around $50).
The spyware/trojan horse angle sounds the most likely cause. I cleaned up a friends computer and their son's computer a couple of weeks ago - both were infected with multiple viruses and multiple trojan horses. Two weeks later and their son's computer is again grinding to a halt. Took a look at it this weekend for them while I was there for a party and sure enough it was once again loaded with multiple trojan horses. He's hooked on downloading JPEGs, MP3s, games, etc. from a number of sites that he and all his high school friends frequent - but the sites require the use of special download and (in some cases) play software which are loaded with spyware, viruses, and/or trojan horses/backdoors. Told his parents that I could clean his PC again, but unless he's going to stop downloading all that crap he'd be reinfected in less than a week. Just in case, I'd already isolated his computer from the rest of the home LAN when I set it up for them so things on his computer couldn't reach out and mess with their other computers. On the Windows Task Manager's Process tab, with nothing else running on the computer, look for processes that continue to use CPU. Note the process names. They could be getting started from the Startup folder or through Registry entries. You may also have to search using Find Files for their names in files in case they're using a launch redirection ploy. Good luck.
ArchAngel, what are you using to get rid of the spyware/trojan horses? My in-laws don't download jpegs or play games online. They do surf the web extensively. Thanks.
hapaboy - The usual anti-spyware/adware stuff didn't clean everything in this case so I ended up removing the remainder by hand
Okay, found more spyware and deleted it. Strange thing was, after I did that the system was running much quicker. The next time it was started, though, it went back to dragging slowly along. Question (possibly a foolish one): With no programs running, in Task Manager and Processes, under the CPU heading, the System Idle Process is consistently scoring between 95 and 99. However, under the Performance tab, when no programs are open the CPU usage ranges from 1 - 3 %. Is that CPU value for the System Idle Process unusual? Thanks again.
Could you decribe how you did that? Some of these trojans run as svchost.exe or another process that seems legitimate so looking at the process list may not help.
An acquaintance suggested restoring the system to a state prior to the problem. Has anyone actually done this? Is data lost in the process, i.e. e-mails and applications? Thanks.
You need to go to www.belkin.com and download a Firmware File via the Belkin Set-Up Utility that will rid your system of the slowness and intermittent connection drops. I had the same thing happen to me ( slowness and drops ) and Belkin put out this specific firmware file in the Fall of 2002 in order to address these issues. No problems at all, since.