Jorge . . . last week my networked, Windows 2000 machine developed exactly the symptoms you describe with the "explorer.exe has generated errors and will be closed by windows" dialog popping up intermittently when I attempted to drill down in my directories--whether the folders resided on the network servers or on my local hard drive. My system was fast becoming unusable, and in seeking a solution I happened upon your query.
The solution my IS guy employed was easy--though certainly not an intuitive remedy, and not the first thing we tried. (We first defragged my disk, ran an anti-virus scan, and ran Ad-aware to check for spyware/malware. None of these actions had any affect on the error problem. Neither did a search on Microsoft's TechNet provide any assistance as its only reference to this error addresses a software conflict that did not apply in this case.)
What proved the solution was to remove an "unknown" item from my Internet Explorer Downloaded Programs folder (a file I had not intentionally downloaded) and clear the cache. Those simple actions set my machine back to rights.
Now that I think about it I am convinced that the "unknown" item we removed from the Internet download file was the culprit that messed up the Windows Explorer function. The night before the Explorer.exe problem emerged I'd been designing CD labels for which I needed an image from the software vendor. I attempted to search for the vendor's website by simply typing the name in my IE address bar--except that I mistakenly misspelled the name. That landed me on one of those bogus search sites that want you to make them your homepage or sell you a domain or whatever. Sometimes, I know from having it happen on my home computer, they'll actually hijack your homepage and it's a terrific chore to get it reset correctly.
Anyway, when I closed that window there was a download window behind it asking me if I wanted to install something or other (some search bar, I think). I clicked "No" and went on with working on my job without further problem.
The Explorer.exe problem appeared immediately after I started up the next morning, and I think now that it was the reboot after the previous incident that triggered it. Perhaps that downloaded software was trying to act like a browser hijacker but was prevented by something in the corporate network configuration or such. Or maybe it was one of those things that try to serve pop-up ads on the local computer, thus causing a lot of interrupts, although that theory doesn't necessarily gel with my having run Ad-aware without finding anything but a few tracking cookies.
In any case, clearing the cache and the unknown download seems to have been exactly the right thing to do--and remembering not to search from the browser address bar in future is a good preventative measure.
I hope this gets to you BEFORE you resort to rebuilding your OS . . . dj
