I've been experiencing that explore.exe is eating up my memory, in fact all available memory and thus causing a severe system slowdown.
I've tried to isolate the problem and I found an explanation related with autorun: whenever I have a popup asking me what to do with the files from hard drives with mixed contents, the system begins to scan inside the file structure and start eating up the RAM. Even if you tell the dialog box to do nothing, it will go on with the process, as if it still searches for items, but it doesn't end.
If I kill the explorer.exe process in the task manager and run it again, the problem dissapears.
But I've found that as soon as I change the Autorun options in the control panel
and uncheck the main checkbox so it doesn't use autorun for any kind of media, it runs as expected.
I'm using Windows Ultimate x64 RTM (build 7600) downloaded from my TechNet Plus subscription.
I also have Mac HFS+ formatted volumes in my system that are read using Mediafour MacDrive. I'll try to uninstall it and check if the problem continues.