If u wanna lock a file with a password ...
u can do so using winrar..
Almost all archives support giving password, including WinZip, 7-Zip and it's not something special with WinRar.
Bt WinRar is more cmfrtble thn any other.
And if you are setting access like this, it is better you set the compression level to "Store", which will make the compression and decompression faster, since the main aim here is to set a password.

1)Right click on the file for which u want the password to b put.
2)Click on "Add to Archive".
3)Then go to Advanced tab.
4)Click on set password...choose ny passwd.
5)Click ok.
6)A winrar file with ur filename will be created.
7)Next u may delete the original file,as u have now compressed it with a password.
8)Any1 tryin to open the rar file wont be able to,unless he knows the passwd.

So, no need of folder lock software.
enjoy ur privacy guys....