I just dealt with this myself. Due to problems with an installation of Windows Vista, I was left with a Windows.old folder that was in my C:\ just taking up vital space.
It was a tricky one, but using a helpful post that I saw here
I was able to get things finally said and done. The key is to use the steps for ADD through to FIND NOW until you get as far down as you can go and then you can select All Access to give you every imaginable access to the files that you can get in Windows Vista.
Hope this helps and isn't too un-informative.
Ok, I made a test folder here to up the informative quality and I'll go through a quick run-down of the process
First you want to right-click the folder or the file and then you select Properties and go to the Security tab and under that you select Advanced. Then in the next window that pops up, you should already be under Permissions tab. Click the Edit button and then click the Add button in the next window. Click on Advanced, then click on Find Now and select the profile that you are using from the list and click OK. Then you are ready to click OK again to go to the list where you will select your permissions. Just select Full Control and you can do anything you like with your files/folders now.