Have a look at CWTYPE.
It is free, and you can connect your paddle to the PC via a serial port (or USB to Serial converter).
You can also connect the paddle via a game port( if you can find one), or a parallel port.
There are circuit diagrams of how to do it in the software's integrated help file.
Also, there are circuits of simple interfaces to provide PTT and CW-Keying for the transmitter.
All in all, a great package, for a great price - free.
You can also use it as a CW keyboard of course, the choice is yours.
You can find it at http://www.dxsoft.com/en/products/cwtype/
It should do what you need.
73 - Rob