Just an example of a problem that had a solution that was a bit different from the norm - thought I'd share
Sometimes it's the things we never think about that can cause the strangest issues.
A friend of mine once had a problem that appeared suddenly where IE would randomly and sparodically open up for no apparant reason. Didn't redirect him to any malware sites, just opened up, same as usual, but without him doing anything. This was a problem he brushed away at first - nothing too serious, just a bit annoying. Then it started happening more and more frequently. Since this was beginning to get a bit annoying, he started poking around a bit to try and find the cause. First off, running a virus scan - nothing. Uninstalling various bits of software that might be buggy and firing off requests for IE to open - no luck there either. He even tried monitoring the thing to see if it occured within a set time, or while any certain applications were open - no correlation at all. It just seemed completely random. Whenever he was using his computer IE would surely pop up a few times at completely random intervals, and was doing so more and more often.
Eventually, he got so fed up he just decided to back up his files, wipe the disk and reinstall windows. He did this, installed drivers and ran updates, and then rebooted to a nice squeaky clean system. He then proceeded to install the software he needed again.
However, before he did, guess what - IE randomly pops up again for no reason whatsoever. In frustration, he whacked his fist down and thumped the desk. IE opened up again. Curious, he thumped it again. And again. IE opened up each time.
After a bit of thinking, he worked out the problem - it turned out one of the hotkeys on the keyboard (the internet one mapped to IE) had a loose connection, and every so often this was making contact and causing the problem. After getting a new keyboard he's never had the same problem again!