ok, do the following and try it.
right click on the desktop, go to New and create a new tText document.
Open the text document and copy and past the following.
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\.exe]
@="exefile"
"Content Type"="application/x-msdownload"
[HKEY_CLASSES_ROOT\.exe\PersistentHandler]
@="{098f2470-bae0-11cd-b579-08002b30bfeb}"
[HKEY_CLASSES_ROOT\exefile]
@="Application"
"EditFlags"=hex:38,07,00,00
"TileInfo"="prop:FileDescription;Company;FileVersion"
"InfoTip"="prop:FileDescription;Company;FileVersion;Create;Size"
[HKEY_CLASSES_ROOT\exefile\DefaultIcon]
@="%1"
[HKEY_CLASSES_ROOT\exefile\shell]
[HKEY_CLASSES_ROOT\exefile\shell\open]
"EditFlags"=hex:00,00,00,00
[HKEY_CLASSES_ROOT\exefile\shell\open\command]
@="\"%1\" %*"
[HKEY_CLASSES_ROOT\exefile\shell\runas]
[HKEY_CLASSES_ROOT\exefile\shell\runas\command]
@="\"%1\" %*"
[HKEY_CLASSES_ROOT\exefile\shellex]
[HKEY_CLASSES_ROOT\exefile\shellex\DropHandler]
@="{86C86720-42A0-1069-A2E8-08002B30309D}"
[HKEY_CLASSES_ROOT\exefile\shellex\PropertySheetHandlers]
[HKEY_CLASSES_ROOT\exefile\shellex\PropertySheetHandlers\PEAnalyser]
@="{09A63660-16F9-11d0-B1DF-004F56001CA7}"
[HKEY_CLASSES_ROOT\exefile\shellex\PropertySheetHandlers\PifProps]
@="{86F19A00-42A0-1069-A2E9-08002B30309D}"
[HKEY_CLASSES_ROOT\exefile\shellex\PropertySheetHandlers\ShimLayer Property Page]
@="{513D916F-2A8E-4F51-AEAB-0CBC76FB1AF8}"
now, close the text document and save it. If you can see the file extension i.e the ".TXT" bit, then rename that so it says ".reg" (without the quotes). Is should then turn the text icon into a icon with blue blocks
Now run that file. It will come up and say that you are changing the registry and are you sure and all that bollox, click yes. That should then re-associate the applications/programs again so you shouldnt get the error your getting.
If you cant see the ".TXT" bit, then open up a folder or "My Computer", Press the ALT key (that should then give you the menu options if it isnt already visible - File, Edit, Tools etc) Choose Tools, then choose Folder Options, then choose the VIEW Tab, then there should be a box ticked for "Hide Known File Extensions" - Untick that then click save and ok and all that so you can then get back to the Text file you created earlier. Now you should be able to see the .TXT extension, so you can now change that to .reg.
Hope this helps and is understandable.