I have a vista ultamite machine that has been running fine for over a year. In the last few months it has started freezing up. Not completely but just explorer.
Any application already started seems to continue working fine, but the start/task bar stops responding along with any windows explorer window.
It can be 5 mins after booting that this issue happens, or up to an hour of so.
This also seems to cause an issue with shutdown also.
I would start by running Process Explorer from Microsoft/Sysinternals. By watching explorer.exe in PE, you may be able to see what part of it is causing the hangs. Could very well be some type of codec/add-in etc crashing or timing out.
Edit: I just came across an amazing tutorial from Kansas State University on using Process Explorer, complete with screenshots (PDF link): Process Explorer Tutorial Handout
I had a client about a year ago that had a similar problem loading some folder content in Explorer. We determined the issue to be one of those all in one codec packages. It was crashing when loading thumbnails in folders containing video files. After uninstalling the codec package the problem was resolved.
Watch the proc explorer videos (at least one to see how to use it)
You don't necessary need to download this extra utility. I'm not a fan of downloading tons of those small tools, what you can do is to utilize the build in Task Manager.
It's a good idea to take a look How to get More Info From Windows Task Manager to Diagnose Your System
Cheers
