You can just go under "window color" from the personalization and slide the slider all the way to the left. I don't know of a way to make the taskbar completely transparent, unless using a modified theme maybe.
My Computer
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Airbot 2.0
OS
Windows 7 Ultimate x64 SP1
CPU
Core i7 920 (D0) @ 4Ghz, *26c idle *65c full load on air
Motherboard
Asus P6X58D Premium - Sata 6Gb/s - USB 3.0
Memory
12GB DDR3 Corsair Dominator -CMD12GX3M6A1600C8 at 1600MHz
Graphics Card(s)
Zotac Geforce GTX 770
Sound Card
ASUS Xonar D2X
Monitor(s) Displays
1 LG 24" Flatron W2453V-PF 1 Samsung 24" P2450H both 2ms RT