Won't get past the loading screen

It's odd that it shuts off after 5 minutes. If you twist around the AC adapter plug when it's connected and on, does it change colors and/or does the computer shut off?

If you have the reinstall media you can always do as Meyer suggests and boot off of it, and I would do a standard install, which will reinstall the OS with your files in place (if you don't choose the option to erase the disk). Hopefully your hard drive is intact and boot files have simply become corrupted, in which case this procedure should replace them and the machine should boot again.

If this doesn't work, rab77hp's procedure may be necessary. After recovering the files (assuming the drive is not bad), you can always put the drive back in and then reinstall the OS.

Do you want to boot it or just get your files off? If all you want is your files then you just need to extract the hard drive. Using this guide, remove the hard drive and place it in an enclosure and you can connect this to another computer and get your files off.

It could be overheating, you might not have fully tightened the screws for the CPU heatsinks when you fixed it, this will cause overheating, and it might not have enough time to boot. You should open it up, and remove the screws for the heatsinks, and put them in, and tighten them evenly.