help .. how to luck my drive c:/ to avoid installing any SOFTWARE not need to my computer.Uh, do you mean LOCK your HARD drive?    

If you are worried about other people besides yourself installing programs when you are not around, you could just enable a password for your system and enable the GUEST account so when guests are logged in they can install nothing,and noone but yourself may install anything

Click START, up at the top of the START menu, click on the symbol/picture thingy, when it opens up, click HOME, then click on your account and make yourself a log-in password (programs cannot be installed unless someone is logged into your account OR enters the ADMINISTRATOR password, LIKE you are doing here), when you are done with that, click on the guest account and click "turn on guest account"...Once it is turned on, restart the computer and you will now see two possible accounts that can be used,  Your account (Administrator) and guest (which does not require a password, and lacks permission to install programs)