C006: Windows 2000 I try opening the Control Panel Add/Remove Programs but I just get an empty window titled res://sp3res.dll/default.hta

Try following knowledgebase 266668 first. If that doesn't work, get the Windows 2000 CD out. Go to E:\i386 or as appropriate drive for your CD. Then run this command:
expand -r appwiz.cp_ c:\winnt\system32\appwiz.cpl or whatever your system root is.