as your project is a PC controlled one..
the segments are likely to be...
The PC Part.. which controls the Robot
The interface - communication btw PC and Robot
The Robot hardware - controller, motor drivers etc
PC part - if you are new to windows API, i'll suggest Serial port with VB. use MSCOmm as akg said. its quite easy...
Interface... serial.. but USB, IrDA,Bluetooth adds class to the project..
Hardware. basically some sensors, and motor drivers..
L298 is a good option if you want less than 2 Amps. other options are L293, UCN5804 etc...
Controller - go for lower pin count ones if you dont manipulate too many variables.. like PIC 16F73..
and make sure u use bypass cap for the motors..
and if you are new to API -
Use VB with MSComm control.. quite easy. for the PC part.