If Hawkeye's solution does not work (and it should)
If you have another computer, or another boot disk
You can boot from another drive and edit the registry in this drive by using "load hive" and "unload hive." This is a VERY RISKY activity. You want to find the key HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices and delete the entry for "/DosDevices/E". It has worked for me in the past; it has made installations unusable in the past. Hope that Hawkeye gets you through it.
Oh: if there is one for "/DosDevices/E", delete that too.