Access Denied to both USB and CD drives

Brand new Dell computer running Win 7 Pro. This is a small office with a network and some servers. I'm by far the most knowledgeable computer guy here, so please don't suggest going to my administrator. There are two people remote from here who put this system together and both hate each other. So they tend to throw up their hands and claim they didn't set it up.

Anyway, last night at home I put some files I need onto a USB thumb drive. Today on the Dell I could see the files, but I could not drag or otherwise copy them onto the HD. Every time I got Access Denied. I tried properly ejecting the thumb drive and that made no difference. I tried rebooting the computer and that made no difference. When I rebooted into the Safe Mode, the files dragged over just fine. A few minutes later I tried the same thing with a CD full of archived data. That data would not drag or otherwise copy. When I rebooted in the Safe Mode it copied right over.

Other computers in the office read the USB and CD just fine. The issue is with this computer and it seems to be different between my login and the Safe Mode. I tried changing the sharing properties on the thumb drive and the optical drive but it didn't work. I've read about this topic on many forums, but it seems the answer is not well known. There are a lot of people guessing at the answer, but not many solved it. I've read the tutorial here about changing the Registry entry to a 3, but mine is already a 3.

Anyone know the solution?

Are you part of a Domain which is applying Group Policy settings that for some reason only block you from accessing the USB/CD Drives? I know the hospital my Dad works in has stopped you writing to CD/DVD's and Unencrypted USB Drives, and only allows their Encrypted USB Drives to be written to, so I dare say it's possible to prevent you copying files from them.

Do you use the same login when you use Safe Mode? I assume you just use standard Safe Mode, rather than Safe Mode with Networking? Any other software installed in the machine that could prevent you from copying files from external media?

You said you tried changing the sharing options, what did you change exactly? Assuming you haven't already done this: what happens if you Share the USB Drive and add your User Account to the Permissions and set it to have Full Control?

Are you part of a Domain which is applying Group Policy settings...
I don't seem to be. Others in the office can open the same CD and USB drive. This office is really not sophisticated enough to set permissions by group policy.

Do you use the same login when you use Safe Mode?
I logged in to Safe Mode with Networking using the same credentials.

You said you tried changing the sharing options, what did you change exactly?
I right-clicked the drive, opened Properties, clicked the Sharing tab, went to Advanced Sharing, ticked Share this folder, opened Permissions, selected Everyone, and ticked Allow for the three boxes. Then I clicked OK all the way back out.