i use 3 hardisk, i have 1 machine on OS HD, 2 machine on external drive and 2 machine on other internal HDQuote:
If u use a normal Hard Drive, u cannot run many VMs.
I have a Dell Inspiron 17r Notebook with an Intel i7 dual Core 2,4GHz, 8 Gb RAM and an SSD Drive.
With this I am able to run 7 stable Machines.
Back then, when I didnt have an SSD i could only run 3 VMs.