what code used to lock Forms like this?
If I intended to crack it, what disassembler? what should i look for? after success disassembler?

Disable all the controls (set the property of each control "Enabled" to false).
Then when user inserts his userName and password validate the data, if all coorect, enable all the controls.

It's not my application, but I'm trying to Disassemble it and make it bypass log in and Unlock All Functions

If it's not your application, then circumventing it or disassembling it might be a violation of the DMCA. Just a thought...