OT - Reverse engineer a .dll & .exe

[aegisx]

It is not illegal is the company owns it.

Reverse Engineering take some time to get good at, but check out IDA Pro. They have a free demo, but if your company is serious about it, they should buy it.

You should know what your getting into though...

There are not really any good tools to reverse it to source code that can compile. You may be able to make a binary change to the dll/exe depending on the change (i.e. byte for byte). IDA pro will not convert it to source code, it will just show you the assembly,objects etc.