Welcome to LQ ... and welcome to Linux! (by the sound of it)
Someone else may be able to advise on recovering passwords for XP. I don't think it's possible. However, if your disk wasn't encrypted, you'll be able to access all your data from a "Live CD" or by installing the drive in another computer. (Is this a laptop or a desktop?)
Do you know which Linux distribution you want to use? And what is the OS of the working computer you're downloading it on and burning it on? - the directions to download and burn really depend on the OS and the burning program more than on the Linux iso itself.
Once downloaded, check that it has downloaded successfully by checking the md5sum published on the download page for most distros. That's a common cause of not being able to boot the resulting CD.
Creating a USB installer instead of a CSD/DVD is another possibility. Does the locked out PC support USB boot?