Re-registering the following 4 files sometimes works :-
1. Start, Run then
2. Type regsvr32 msscript.ocx in the box and click OK.
3. Repeat number 2 above replacing msscript.ocx for the other 3 files: dispex.dll, vbscript.dll, and scrrun.dll.
Next, make sure file (open) type .JS is properly associated :-
In Control Panel, Folder Options, File Types locate the .JS extension and click Advanced, then Open, Edit and make sure the "Application to perform action" field contains: C:\WINDOWS\System32\WScript.exe "%1" %*