Just FYI, you may have administrator priviledges but with the added security in W7 you are not the administrator on record as owning the system files. You may be the only administrator visible but there is actually a hidden administrator account (with no login priviledges) that is given ownership to the windows files.
The first step I recommend is go to control panel \ user accounts
1) make sure it says you are an administrator
2) find the option at the bottom "change user account control settings" (also called UAC by microsoft). See at what level this is set. I have mine set to 0, you might try this and then see if you have access. Once you finish what you need you might set it back up to 1, maybe 2.
If that didn't solve your problem, the utility program Core linked to will allow you to assign access for your account to the files and folders BUT I wouldn't TAKE OWNERSHIP from the C: folder of every file; instead do it in stages, because from C: would run a long, long time as it dives into subdirectories. I would probably start with Documents and Settings and even that will run a pretty long time. Then try what you need again and if that doesn't give you the access you need, come back and let us know what it is doing, what you've tried and what happened so we can further evaluate.
