So, my laptop has gone kaput. Luckily, the hard drive was salvageable so all my files are still intact. I can't replace the lap top currently due to cost, but I was able to get a caddy for the drive and can now utilize it as an external drive. What I need now, is to be able to boot my other computer from this external usb drive. I'm not sure where to start exactly, so any suggestions would be helpful.

If you are thinking to run Windows from that external drive I don't think that is going to happen. That is be MSoft design. You should be able to access the drive to recover files from an different computer. You will need to take ownership of the files though. To take ownership look at the link below. http://support.microsoft.com/kb/308421

Just get a live linux cd. Boot the new/other computer to that OS and read files. Might just be able to take ownership of folders . I read it wrong and answer it wrong too. So get off my case you peanut.

Eching the above posts... Two Linux on a CD variants are: Knoppix and Ubuntu. Each is available on CD for small cost, or can be downlaoded as an iso - which then burn to a CD. When you boot up with the CD you will then have access to whatever is attached to (sub etc) or physically in the system. You may have to change boot order to allow the CD boot option?

At any rate you aren't going to be able to run WinXP off the external like it worked when it was an internal drive. Knoppix is GUI interface and has many opensource programs included so you may be able to do some work with it. Going back to your original post, why do you feel you need to boot from the old drive?

The issue isn't booting internal or externally, you can do that. Issue is Windows registers and loads drivers particular to the system it is installed in. You can not just move a drive to another dissimilar system and expect it to work just like it did in the original system. Your option is to access your data via the various methods mentioned above though taking ownership of all the files from the system you are presently using is all you really need to do to access your data on the laptop drive. Imagine the power if you knew how to internet search