You have to take ownership of the drive, so you need to be an administrator account.
If you right-click the drive, choose Properties, and select the Security tab. If you don't see the security tab, you may not be an administrator account, or you may have Win 7 home instead of Pro.
In any event, if you do have the Security tab, look at the Groups and users assigned. Since you want access for only yourself, you'll have to take ownership through the Advanced button, Owner tab. Once you change owner, close and re-open the security settings and change the names in the group/users box. You'll want to change owner and permissions recursively, to effect all the subfolders and such. OR once you take ownership and get access to the drive, you'll have to go through the same procedure for subfolders.
This was the quick and dirty answer to get you started. Let us know what turns up.