Do you have lots of pretty Red X's in your Event Viewer?
Anything could be causing Explorer to crash. You might consider recent updates. Also consider any other changes you have made. Corrupted files can cause this too.
To get further information about your errors look in your Event viewer.
Look in the System or Application folder. You can get to the Event Viewer via right click My Computer icon and select Manage.
Any errors logged in the Event Viewer can be expanded by double clicking on the error line.
Take any event error I.D. number and search for it on this site.
Also check any "Information" line that mentions "savedump" and you should find reference to "recovered from a bug check". This is the Stop Error message.
You can also turn off "automatically restart after an error" so it will just halt at the fault and display the full Stop Error and blue screen.
Right-click My Computer, and then click Properties .
On the Advanced tab, click Settings under Startup and Recovery .
Click to clear the Automatically restart check box under System failure , and then click OK . The error message on a blue screen should remain on the screen so you can record the error information.
If you want the highly technical cause of any crash look in the Documents and Settings/ All Users/ Application Data/ Microsoft/ Dr Watson/ Drwtsn32.log
Find the entry that is relevant by date and time to the crash you are investigating. The exact cause of the crash is indicated by "FAULT ->" on the left of page next to line of code causing crash. This, if your as cluey as me, wont tell you much but you can use it to see if it is the same fault all the time, and further up the log you can find what processes and modules are running.