looking for a descent troubleshoot tool

Hi Guys

I am looking for a descent troubleshoot tool that will work from stiffy, Linux, UNIX and Windows??
I am a technician new to the trade and my work demands that I must troubleshoot dumb terminals as well as PC?s to see if all the hardwareis ok!! The hardware is usually the basics like display card, network card, line ports, serial ports, CPU, burn in tests on the PC?s and some other controllers.

I would appreciate help very much

Thanks
Melt
meltvn@mweb.co.za