at least use a 9V square battery for the supply, dude. It can show better results. 3.3V from laptop ports are for low-current applications. motors use much more power, and draws much more current.
I use a 12V 7Ah battery as Vcc to the IC. I've tried both 3,3V and 5V as logic Vs but neither works. I've also changed to 2N3904 transistors, still doesn't work! What could be wrong?
The 7805 need 2 small capacitors that are not shown in the schematic. See the datasheet. Using a buffer, maybe a 74HC14 betwen the port and the L298 would also help.