[Simple]

@lurchy666, Your computer is not screwed up, and the process works... Also this process works:
http://cartechnology.co.uk/showthread.php?tid=13539 It has an attachment that has links to a collection of downloads.

Can you check that you have all the files in the cache folder? if you make a mistake, DiagBox deletes the contents of this folder, you can copy the 13 needed files or use the "Cache Contents Restorer" in the links to replenish the contents.

If you have renamed your working "C:\AWRoot" of your DiagBox 7.57 or above to "C"\AWRoot7" and it has working APPDIAG.SYS, CFG.BIN and CONFIG.SYS files, then download and execute "AWRoot_v7_Conf+Ativation_v8.exe"; your DiagBox 8.01 should then work..