How can I capture HDV and SD from my JVC GY-HD100?

I have a PC.

Several tools can capture the M2T data, but only a few can do any editing of the 24P mode from the GY-HD100. This will change over the next few months as video editing tools companies have more time with the camera. Currently only Sony Vegas and Premiere Pro running Aspect HD will support all the capture modes of the HD100 on the PC.

Do I need to have SP2 installed for Aspect HD to find the cam?

SP2 is strongly recommended but not required. Camera drivers for SP1 are somewhat painful to install, one you get them installed Aspect HD will work fine.