AVG doesn't work on my computer. I don't know why, and I don't care, I just want all of this crap off of my computer. My computer has so many AVG files that are worthless, and for some reason I can't delete them. Any help?

Have you even uninstalled it yet? Or did you just go ahead and delete everything in sight?

I can't delete anything, that's the problem. I also uninstalled it a long time ago, but it still takes up a ton of memory.

It's been this way since 2009.

Time to turn to extreme measures.
1) Cut the remaining AVG files, along with a few huge files, to a USB. While the files are being transferred, quickly unplug the USB from the comp. The files will hopefully be dropped onto the ground and out of your comp.
2) If that doesn't work, unassemble your whole computer, sterilize all the hardware except for your memory cards and your HDDs, burn the mem cards, HDDs and the computer case with lava (make sure there is nothing left but ash), then buy a new computer case, new HDDs and new memory cards to assemble a new computer. If all of the AVG files were on an external HDD, you may spare the other HDDs.
3) If AVG returns to your reassembled computer, say goodbye to your home, buy a new house, put your current house on fire, move all the non-electronics belongings to the new house, move all the remaining family members and other lodgers out of the house, then bombard it with napalm. Then buy a brand new, AVG-free computer. If AVG mysteriously reappears in your new computer(s) after a few days or weeks, then it is safe to conclude that it is too late as AVG has successfully infected you with it binary genetic code, and you should suicide after obliterating your new house, with all the occupants of both your old and new houses in it, with napalm, convincing yourself you've done a good thing by exterminating from the Earth a would-be world destroyer.

Search for "msconfig" or go to C:\Windows\System32 and open the program. Click the startup tab and then find AVG, that'll stop avg from starting up on its own.

I have already uninstalled it, but the crap is all still there, taking up space. I've tried many things, it just won't go away.

If you can't delete a file, usually it's because that program is running in your memory. Xboi's telling you how to prevent AVG to automatically run on startup, so that you can delete the files after rebooting.