Motherboard fried, need files off of HDD. (SATA to USB)

I opened it up and tried to backup the partition that I needed. It said it could not find the file specified.

Right click on My Computer and go to Manage. Scroll down to Storage then Disk Management. See if you can find your external drive listed on the right.. It might be Disk 1, 2, 3 etc and listed as blank or unformatted. Right click on it and see if you can assign or change the drive letter to an unused letter to make it visible.

Easeus also has a few other free data & partition recovery programs you could try. Haven't used it, but I would try the partition recovery program first. The data recovery program is good, but extremely time consuming.

Well it had the partition on there, and I selected it to start the backup and that's when it said that it couldn't find the files. I will try the partition recovery tomorrow. It's getting late. But do you think it would work in my desktop still if I just replaced my motherboard?

I'm not sure. It really sounds like there is a problem with the partition table or a file table on the hard drive. Those USB connectors usually work well as long as all the connections are good. I use one regularly for data recovery on client's hard drives.

You could connect that hard drive to any desktop computer as a secondary drive and Windows should read it, as long as the drive is good. Try the connector and external drive on someone else's computer and see if you have the same problem. Or test a different external hard drive with the cable if you have access to another drive. That will help isolate the problem to the cable, drive or PC. My guess is your drive.

If no dice, move on to the free partition or data recovery software since you have nothing to lose. Maybe someone else will chime in if they have a better idea.