Even with CoolBits enabled, you're not going to get sideband AGP working. You will get control over the core and memory clocks, and ability to control / disable VSYNC.
Put the following lines into a text file and name it "coolbits.reg" (everything between the dashed lines, but not including the dashed lines):
-----------------------------
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\NVIDIA Corporation\Global\NVTweak]
"CoolBits"=dword:00000003
------------------
Save it, then double-click it to enable coolbits.