Do you know how to get into your BIOS (CMOS) setup program ? Typically it's something like press DEL as the memory test starts or a ctrl F? combo. In the bios I suspect someone has turned on the anti-virus protection "feature". This will stop any software from accessing the boot area of the hard disk. Disable that (assuming it's enabled) and try again. In Safe mode with a command prompt I don't think autoexec or config.sys are processed so it's down to something like this.

We will get you there but heck it's hard by remote control !!

Ingmar