Windows 7 - New external - need to delete files without admin approval?

Hello, new here obviously. I am trying to get my new external synchronized up with my current laptop. I had a Dell Studio 17 and I'm now on a new (read: crappier) Gateway computer because the old one broke.

I finally got around to pulling the hard drive and getting a case for it so I can access some books for games I play, and I'm having a problem deleting some of the system registries that I obviously don't need. I have tried but I can't, do to the operating system still active on the hard drive. I have been clicking out the older files that don't require admin approval from my old laptop to delete. It would make my job a lot faster if I could just delete the entire Program Files and PF x86 folders.

So, first question is, without reformatting the hard drive, can I delete these admin-protected files?

Secondly, is there an easier way to weed out the unneeded files (all 120 gigs of them) without wiping the entire thing.

I'd bring the files I want onto my current baby, but it has a MUCH smaller hard drive (I'm going from 500gb's to 320, 280 of which are available ).

P.S: Sorry if I put this in the wrong place. If so, I won't be mad if it's moved - just makes my job easier.