You don't say which particular places it is, that you do not have access?
In your own interests, and as a result of voluminous feedback from beta testers and the public, Microosft have tightened up the accessibility to system files and folders. It is quite straightforward to alter the security on most of these, but would serve no useful purpose.
Windows 7 and, previously, Vista, have advanced quite a way from XP, and a lot of work has been done on nackwrad compatibility. This has , unfortunately, also resulted in the introduction of "junction" folders. Basically these are old name folders inherited from XP and previous. Many small software makers, cannot spare the effort to change paths for their installations, so these folders exists purely for that purpose. Files directed to those folders, are now redirected to the more appropriate Windows 7 paths. A classic example is the old "Documents and Settings" folder. I fairness to Microsoft, if you accept the "Tools - Folders Options - View", defaults, in Windows Explorer, you should not even be able to see these "junctions".
However, you can become the "Global" Administrator, which is what you have been more accustomed to in XP. This lowers your security warnings but, if you feel your own third party security is adequate, it is not a great problem.
There are a couple of ways to achieve this:
Open a command prompt(Run as Administrator.
Type the following command and enter.
net user administrator /active
Log out and see if you have a new alternative (Administrator) login, as well as your existing one. If not, do it the long way.
Shut down the computer for a cold boot. Tap the "F8" key as you are booting.
Select "Safe Mode with networking" from the boot menu.
Log into windows 7 with your personal account that holds the administrator access.
Open a command window (START--->RUN--->CMD.exe). At the command prompt type the following net user administrator /active
Log out and log back in as administrator.
Another way
Go to Start
Type Control UserPasswords2.
Click Advanced.
Click Advanced again.
Select Users.
Select Administrator and untick the the box “Administrator is disabled”
Now log out and login as Administrator.
As I previously said,the action leaves you a little more vulnerable to outside attack. Not a big issue if you are confident with your anti virus control etc.
You can also take control of any file or folder you wish, by applying the attached registry edit. This will give you a right click option to "Take ownership. Use it with caution.
I use the above suggestions as my default. I have a disabled guest account and nothing else. I have also wound the UAC down to the bottom, disabled Windows defender and the security centre. This is only something to do if you are totally knowledgeable of security risks.