Need suggestion in how to set up Windows Server 2008 R2 with Hyper-V

[peterc_shop]

I want to set up a testing machine using Windows Server 2008 R2 with Hyper-V.   Here is my machine information:

HP Pavilion Elite e9150t PC
•  Intel(R) Core(TM) i7-920 processor (2.66GHz, 1MB L2 + 8MB shared L3 cache with QPI Technology)
• 6GB DDR3-1066MHz SDRAM [3 DIMMs]
• 640GB 7200 rpm SATA 3Gb/s hard drive
• 1GB ATI Radeon HD 4650 [DVI, HDMI, VGA]
• LightScribe 16X max. DVD+/-R/RW SuperMulti drive
• Wireless-N LAN card
• 15-in-1 memory card reader, 1 USB, 1394, audio
• No TV Tuner w/remote control
• Integrated 7.1 channel sound with front audio ports
• HP 2.1 30W stereo speakers with subwoofer and remote control
• HP multimedia keyboard and HP optical mouse

I mainly use this machine to test SQL Server.  I will also try other MS products like SCOM and Sharepoint.  I may want to try out VMware since it is quite commonly used.   I also want to try out RAID and Clustering.

Since I only have 1 SATA drive, should I partition it into 2 partitions, one for host OS and one for VMs?  If I have one partition for the host OS and if I need to reinstall the OS for any reason, how should I do it so I don't need to reset up all the VMs again?

I have a spare IDE 80G drive but I'm not sure whether I can add it to this machine.

If I'm going to get another drive later, what should I get and how should I set it up for my purpose?

Thanks for any suggestion.