I'm not going to lie, the majority of this post falls under the category of tech support, but if someone is kind enough to help out, I'd appreciate it. There are three major issues at hand. The other day, I decided that I don't want my old PCs to rot, and now that I have an external hard drive, I was thinking about repairing them. With one computer, the internal disk drive is corrupt, and I've had no luck booting Ubuntu from my External Drive via USB cable (Ubtuntu is installed on the drive, ATM). As for the other computer, either the power switch is broken or there is something wrong with the computer PSU. If I cannot fix either of them, I was thinking about taking my GeForce 4 out of one machine, and using the monitor of the other machine to setup a dual monitor*. For your convenience, I will break the post down into sections: Booting Ubuntu from an External Hard Drive: I posted on the ubuntu forums and inquired about booting Ubuntu from an external drive, but I didn't receive much help. Originally, I was going to try and install windows on the drive, but windows did not have permission to partition the device. I later read that windows cannot run off of a USB device, so I abandoned the idea. I instead installed Ubuntu on the drive and was able to boot the OS on two different computers by using grub and super grub. However, I ran into a problem with the computer that had a corrupted internal HDD. Not only could it not boot from a USB device, but it did not recognize the drive. I tried updating BIOS as well as booting from grub and super grub. No dice. I was thinking about getting FreeDos and trying to boot Ubuntu from there, but I do not know if FreeDos supports USB. Is there anything I can do, or am I out of luck? No Power? So, a few years ago, my dad's computer started going haywire. Occasionally, the power button wouldn't work, and then one day, the computer wouldn't power on at all. I thought it might have been the outlet or the power cord, but it wasn't. I opened up the case earlier and dusted everything off, but I really don't know what I'm doing in there. After touching grounded metal, I found the area where the on/off switch connects to the computer's PSU, and it was a bit loose. However, it didn't seem loose enough to be the source of the problem. Is there any cheap way I can fix this? How can I diagnose the problem? All is not lost If I cannot fix these two machines, I could still use a few of their parts. I want to take out my GeForce 4 and plug it into my current computer, but I think my graphics card (GeForce 6150LE) is better. Can I plug in both cards at once? If so, can I choose which card the computer should use? Would their be any problems if each monitor is plugged into a different card? Thanks in advance, fellow programmers and developers! *Normally I would just plug the second monitor in the back of the working computer, but there is only one plug.

No, you can't use the GeForce 4 and the 6150LT at the same time, unless one of them is PCI. The GeForce 4 is definitely AGP, and AGP motherboards only have one AGP slot. There are "SLI" PCI Express motherboards that have multiple PCI Express graphics cards, but that won't help you with an AGP card.

For the power supply problem, I would first try to re-seat all the cabling, including looking for loose connectors (missing fan connections may cause it to not start, for example). You could also try wiggling the voltage selector and power switch on the back of the PSU. I would also check the fuse on the power supply. If that doesn't work, I would break out the multimeter and see whether there is connection from the power button when it's pressed, or whether the button is out.

Assuming all of that checks out, then if the power supply is a standard ATX mount power supply, you can buy a new power supply for about $40 from newegg.com, and replace the old PS. Power supplies do die at times. Just make sure to get one with the right power connectors for your motherboard -- 20-pin or 24-pin? And 4-pin or 8-pin CPU power? (A 20+4 pin connector might be safest)

Thank you, Sir!

I was beginning to think I had a few bricks on my hands. I'll investigate the PSU problems ASAP.

Another option is to buy an entire new case with power supply. That will make sure you get a new power switch, as well as power supply. There are tons of options; check http://www.newegg.com/Store/Category.aspx?Category=9&name=Computer-Cases for example.
Make sure you get a separate power supply if the case doesn't come with a power supply, though.
And, again, this is assuming that all the components use standard mounts (typically called "ATX").