I am a Windows administrator on Windows 7, but am unable to access any of the folders that have a lock icon. What do I need to do to access these folders?

is this computer in a network?
if so try to login as the computer administrator rather than the network admin

if the computer is stand-alone no network, then make sure you login as administrator not as a user with administrator priviledges

close your windows explorer and start it as "Run as Administrator".  

Hang on.... that perfectly normal
Yes, there are "hard links" on your system (the folder icons with a lock) that are not available (even for an administrator account).   This is perfectly normal, and is by design.
Most of the these "hard links" are designed for backward compatibility... for example, you'll find a old-sytle "Documents and Settings" folder in the root of the C: drive.   This is a "hard link" to the C:\User folder.  Interactive programs (like *you* logged into the shell) should never attempt to traverse those directories (since you're supposed to know better!).  However, applications that have a hard-coded path to "C:\Documents and Settings" can still work.
Relax and enjoy Windows 7

My 2 cents on this..... I agree with graye.... You will not gain anything messing with these folders.... I have done it just for kicks and it is exactly what he described to you. They do not contain anything that you need or will need to modify at the moment.
Bits.