Edit: Thanks for all the help, found a BIOS version and updated them all and gutman'd them all. everything is working well and nothing has died so all my paranoia paid off... or there was nothing there in the first place and it was a waste of time :D haha but thank you guys for all your help, was a good learning experience at least :)
I have looked around and read a lot of people saying it's difficult to be sage when dealing with a second hand pc. But thought I might give the situation to you guys and see what you guys think is necessary to do.
I have just purchased 3 old school computers ( this is what I am told they are used for and one booted with department of education warnings) so it seems safe so far. I am currently running KillDisk (gutman) on them and then following to install Linux.
One of them is going to be scraps for testing a few old pcs I have that aren't working to see if I can fix them.
One will be for me to learn and practice using a Linux set up.
And the last will be for my sister to use to practice her typing.
Ideally they will join the network for updates and my practicing and also in future for my sister once I know what im doing on Linux.
My only concern is will the network be safe after gutman and Linux install. Honestly I think I'm looking for peace of mind but if there are tips and tricks I use please suggest. Ideally want to get one of them up and running for my sister as soon as possible (this won't need the Internet... yet)
Mostly a bit sceptic due to the price($10 each) but they seemed to just want to get rid of them as they are quite outdated( C2D desktop)
Thanks in advance I look forward to your thoughts and opinions and the occasional tin hat joke :)