The general advice when you delete something then find you need to recover it is, "STOP using that hard disk", immediately.
Take the disk out, and either take it to a professional data recovery engineer, or if you are going to attempt a recovery yourself, install it into another system or some USB enclosure, and then try to recover the files.
Why? The more you use that disk, the more likely you will overwrite important information on the disk. Data recovery is always going to be hit or miss. Sometimes you fall lucky, but sometimes not.
I deleted a few .mpg video files from my computer and have used a few different file recovery programs (File restore profession, recuva, Undelete). However, on most of them, these files do not show up on the list of files I can recover (although may of the other .mpg files I've deleted in the past do show, some of which are unrecoverable). Why is it that I can't get see these large 1gb files to show up? Are there any better alternatives to recovering the files?