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Under pu circumstances, you should find a friend that has a working computer and backup al your computer using his computer as the 'master' and the drive from minicomputer as the 'slave.'
An alternative would be to obtain a backup program that boots fro a CD and can backup material from lyou internal drive to a external.
One of many commercial products is Acronis Backup & Recovery
Acronis server backup & system recovery software. Download free trial. www.Acronis.com
Of course, a working PC is needed to create the recovery CD. You say you already have an external drive. I think the Acronis product does have the ability to copy an image to an external drive.
The above ideas will work if the PC hardware is alright. The assumption is that the operating system has been damaged and for some reason you do not have the proper recovery CD that every computer user ought to have at hand.
FYI avoid a USB hub for external drive. USB hubs often are a source to trouble.