Garrys Mod graphics settings are limited?

[AmuletOfNight]

Hello, I cannot seem to take my Garry's Mod shadow detail above Medium (That's all that shows up). Is there any way to get it to high? These are my specs:

Summary
Operating System
MS Windows 7 Ultimate 64-bit SP1
CPU
Intel Core i7 @ 2.00GHz 54 °C
Sandy Bridge 32nm Technology
RAM
8.00 GB Dual-Channel DDR3 @ 665MHz (9-9-9-24)
Motherboard
Dell Inc. (CPU) 54 °C
Graphics
Generic PnP Monitor (1920x1080@60Hz)
(Illegal Vendor ID)
Hard Drives
625GB TOSHIBA TOSHIBA MK6461GSY ATA Device (SATA) 41 °C
Optical Drives
HL-DT-ST DVDRWBD CT30N ATA Device
Audio
Realtek High Definition Audio

I have the latest NVIDIA drivers for my card, which is an NVIDIA GT540M.