I was also thinking on the lines of FORMAT with the Q and U switches!
Some of the IBM techs are really fast at setting up an unsuspecting victim's machine with fatal type practical jokes!!!
Never leave any "Non-Client" machines unattended while the big blue gurus are lurking about
Some other quick mean tricks:
1: Using a text editor, delete the boot signature [first 512 bytes on fixed disk], "DELTREE" the drive, delete or edit the boot strings, delete or edit the file "MSDOS.SYS" on the primary drive, and a few other things.
2: From a DOS prompt, do the before mentioned Disk Format procedures, or delete primary partition with FDISK.
3: Go into the CMOS (ROM BIOS) Setup utility and tweak the drive setting, or tweak the security settings. Lots of fun mean things can be done within the setup utility, which will leave a person with a machine that seems all but usable.
I have only done a few fatal pranks, and do not encourage anyone to do such practice! The circumstances justified the fatal tweaks, which is why they were done! [long, loooonnnngggg story!!!].
Have however been the lucky Tech guru guy called in (many, many, MANY times!) to fix many machines which fell victim of cyber hack clowns [joker EEs].
Been a while since getting those frantic phone calls, so maybe this thread is a precursor???