BleepingComputer.com: Tricky infestation

Hey everyone, I'm new here, and I have a problem with my computer that I have been unable to solve on my own. I have a Dell Vostro 1500 laptop running Windows XP Professional SP3. I've had viruses and malware in the past, but I've always been able to root them out using various programs. This current infestation simply won't leave. Here are the symptoms: when I re-start my computer, once my desktop pops up and sort of "loads itself" (all the various tray icons appear, internet connectivity is established, etc.), I get a Windows error box that says "Generic Host Win32 has crashed and needs to close" or something of that sort. Once I close the error box, two things happen. First of all, my sound stops working. Secondly, the round, bubbly Windows XP shell disappears and becomes replaced by the boxier, more basic looking shell reminiscent of Windows 95. When this happens, I have figured out that I need to open Explore, go into the Dell drivers folder, and reinstall driver R171789 (which is apparently the Symantec Audio Driver, or something). Once I reinstall it, audio functionality returns that the shell goes back to normal. I have to do this EVERY TIME I restart my computer. About once out of every five or six times, this procedure doesn't work. At this point, I have to restart my computer and try it again. Upon the second try, it always works. So this problem is manageable, but the fact that it keeps happening is kind of annoying.

Next, I experience problems with internet connectivity. About one time out of five, when I restart my computer, my internet won't work. The wireless network is recognized, but the connection process doesn't finish. Usually, restarting my computer solves the problem. When I take my laptop with me to another place, with another wireless network, I usually have to restart my laptop once I'm there in order to make use of the new network. Again, this is manageable but annoying.

My final problem, which may or may not be related to the first two, seems to be a common one these days. Basically, when I click on a search result in Google (or any other search engine), it usually redirects me to some ridiculous advertisement. If I back out of the advertisement and click on that particular search result again, I get taken to my intended destination. Clicking on another search result within the same query, or the same search result in another query will once again bring up the redirect. Interestingly enough, the redirect does not happen when the search result is a Wikipedia page. Again, this is manageable but I don't like it because it clearly is not supposed to happen.

When I encountered this problem, my computer was equipped with a free trial version of avast! anti-virus, the free version of AdAware, and Malwarebytes as a passive scanner thrown in to get a bit of variety. None of these programs, even fully updated, were able to find any infestation in my computer. I even created a custom scan in avast! that was as stringent and thorough as possible, and it still found nothing. Frustrated, I got rid of AdAware entirely, and replaced avast! with a free version of AVG. The AVG didn't help either, but that is what I am currently running. The January Windows Update package came with the most recent Windows malicious software removal tool. The tool informed me that my computer had an infestation, and that I should run it. I ran the tool, and it didn't find anything.

This is the situation I'm in. I'm sorry that this post was so long, but I tried to be as specific as possible. If anybody has any insight into my problem, please let me know. Thanks in advance for your replies.

Edit: Moved topic from XP to the more appropriate forum. ~ Animal

If anybody is interested, I ended up eliminating the infestation and all of its symptoms by using TDSS Killer, a tool that was recommended in another thread on this site. My problem is finally fixed!