If not hardware, but “only” software is malfunctioning – try SystemRescueCD, a Linux-based recovery CD/DVD/Flash stick (it all depends on how you burn/install the downloaded file – manuals and how-to’s are available).

As always, Disclaimer: I am in no way associated with SystemRescueCD, and gain no profit from this post. Any advice I give is provided AS IS, with no guarantees of fitness to your exact case.

It does exist – Ultimate boot CD. That CD has numerous freeware testing and diagnosing utilities which will help you – if you are up to some good old (read “small fast”) DOS utilities. And not that old, actually – modern hardware is supported.

The only modification I’ll do to the Ultimate boot CD will be adding freeware bin/hex viewer/editor. Surely, more utils to come – with original size of just 115MB, there’s plenty of room to add extensions. You can even extend the CD image with non-free software, like Partition Magic.

P.S. To diagnose and fix software problems – have a look at System Rescue CD.