windows task manager
ctrl alt and delete
when it opens
click on file (New Task Run)
copy and paste this in runhttp://www.dougknox..../file_assoc.htm
then try a system restore
using task manager file new task run
copy a paste this
It may even occur that you cannot open regedit.
To fix this, open task manager (Ctrl-Alt-Del) and click on file - new task while holding down the control key.
This will bring up a cmd console. From there type regedit.exe and the registry editor should open.
If you have got this far, all is going good
Go to this webpage:http://www.dougknox..../file_assoc.htm
Here you will find lots of registry files to restore the file associations.
Download the ones you need and import them into the registry through registry editor.
This should fix your PC enough so you can perform a repair or system restore.
In all reality, the only full solution is a format and re-installation of Windows here, or a full restore from a backup image (e.g. a brand name PC's recovery disk). you could try the above