1. try safe mode. it should not load any components besides the absolutely basic ones. then you should be able to install/uninstall pretty much anything, including directx:
To get into the Windows Vista Safe mode, as the computer is booting press and hold your "F8 Key" which should bring up the "Windows Advanced Options Menu" as shown below. Use your
arrow keys to move to "Safe Mode" and press your Enter key.
Note: With some computers if you press and hold a key as the computer is booting you will get a stuck key message. If this occurs, instead of pressing and holding the "F8 key", tap the "F8 key" continuously until you get the startup menu.
(from:
http://www.computerhope.com/issues/chsafe.htm#03 )
2. use sysinternals tools to find out what process uses the dll.
http://technet.microsoft.com/en-us/s...c5a693683.aspx
3. use task manager to kill running processes or msconfig from the command line to stop processes from being started at bootup
if you have no idea what this might mean, don't try it! (sorry, not meant in a disrespectful way, it's just that you might mess up a lot).