For those of you Windows 7 that don't know, the default administrator that used to be on Windows XP still exists in Win7, but it is hidden and deactivated by default. This makes any computer running Win7 100% vulnerable to on-site attacks, all you need is a Win7 installation DVD (not startup repair, the actual install disc).
Say you're at school using a computer on a standard user account that has no administrator rights or privileges. If you're like me and want a clean desktop, you need admin rights to delete certain icons like flash player, java, etc. If you want to install a game/program to that computer, you need admin rights. If you want to allow the computer to update the java to get rid of that stupid pop-up saying there's a new version of java (cuz you know the school's not going to maintain them..), you need admin rights. So you happen to come across a Win7 Installation DVD laying around in you're computer teachers desk, go ahead and borrow it for a few seconds.
Step 1: Shut down the computer.
Step 2: Boot the computer from the disk. (tip: after you choose boot from disk, get ready to press any button, as it will flash across the screen to push any button or it will skip to normal boot)
Step 3: Choose language and OS
Step 4: Click "repair you're computer"
Step 5: Choose to repair it using various tools (not sure of the actual wording on that, but you get the point.)
Step 6: run CMD
Step 7: type "net user administrator /active:yes" and hit enter
Step 8: type "net user administrator password" and hit enter (substitute "password" for whatever password you want)
Step 9: Take out the DVD, reboot the computer, log on as the administrator
Step 10: Have fun with you're new admin account
This only works on the ONE computer that you did this on, so if you're working with a huge network of computers and you want to be able to use this account on all of them, you have to do the same thing to all of them.
OR
Once logged on as the administrator, add you're real account (or create a new one) to the administrator's group and give it all the rights possible.
Kindof a herp-derp no brainer, but sometimes people are so focused on the awesome bad-ass hard way of doing things that they forget that there IS easier ways to do things. If you don't have access to an installation disc at all, download a Win7 ISO or IMG file and make one. The rumors about those discs not working because the disc doesn't have the protection seal on it are false, I've done it a number of times. This method is also very discrete and it's impossible (unless I overlooked something) to tell that the account was ever activated or used unless somebody is specifically looking for the usage of that account.