Clean up after upgrade

I just upgraded on a machine that was new 6 months ago. I built the machine, put xp on it, and then used the win7 beta up until now. I purposely had nothing on the computer that i would want to switch over once i installed the full windows 7. But i know things are somewhere since the disc i got was an upgrade and not just the full install software.
am i able to safely delete the files that are windows.old and windows.old.000? it's about 24gb of space, and should be things i don't need. But when i start to try it says ... is a system file, things might not work at all or correctly if removed. Can i just say delete anyways? and is there anything else i can get rid of?

Yes, you can safely delete the windows.old files. Windows is kind enough to save them for you in case you weren't smart enough to back up your data when upgrading. In that case, they would still be there for you to rescue.

But in your situation, if there is nothing in there that you need, you can delete them safely. Windows does not use any of those old system files to run. They're just the extra baggage that gets left after an upgrade (like I explained above).

You can even use a program like File Shredder to completely get rid of them (unnecessary, but possible).

Don't forget to back up your computer before and after you do anything important (do it on a schedule, too)!!