I suspect that you are not dealing with locked folders, but with files that won't open.
In all likelihood (given the message you describe) you have downloaded and installed a ransomware virus. These viruses encrypt your data files and demand a ransom for the key to unlock them. The most (in)famous one of these is Cryptolocker. Google for 'ransomware' and 'Cryptolocker' to learn more, there's too much to tell in this post alone.
The malware wants you install the Tor browser because that way you can pay with bitcoins and the server that you have to visit (to pay) can't be traced.
If it is Cryptolocker, you lost. The Cryptolocker encryption is unbreakable. The only thing you can do is reformat the hard disk(s), reinstall Windows and restore your data from back ups.
Do not (attempt to) pay to get the decryption key:
The bad guys may give you the key, or they may just take your money and not give you anything. The Cryptolocker gang did supply the keys initially, but I'm not sure that they still do, because everybody is going after them.
With computer security people going after Cryptolocker, (intermediate) servers are taken offline so they may not even be able to supply you with they key anymore.
Do you really want to pay these crooks? That's only an incentive for them to go on.
If it is a more recent ransomware virus, maybe something can be done, but with the little information you gave this cannot be determined.
For extended technical discussions on the workings of Cryptolocker, listen to (parts of) Security Now episodes 427, 428, 432 and 439 (or read the transcripts you can download there).
EDITED TO ADD Aug 2014:
There is now some hope for unlocking Cryptolocker encrypted files with the decryptcryptolocker site provided by FireEye and Fox-IT.