Hi, I just got a new PC with following configuration and have made 9 partitions on my 500 GB hard disk and have 2nd 500 GB HDD as slave with 2 partitions, one has Win -7 Ultimate & 2nd partition is where I store Movies & Video Files. The OS Partition is 100Gb & I have installed all applications in OS Partion. All the applications with Win -7 Ultimate 64 bit has taken up 50 GB space. I do download some stuff everyday & it goes in Downloads folder & takes up upto 25 GB of space. Thus I am left with 25 GB free space. In order to have a lightening fast performance, how much free space should I leave in the OS Partitions ? Here are the specs of my system : Intel Core i-7 2600 Sandy Bridge ( 3.4 GHz ) Processor 8 GB DDR3 SDRAM 1333 MHz Windows -7 Ultimate ( 64 bit ) 500 GB Sata 3.0Gb/s HDD Second 500 GB HDD which I am using as a slave drive to store Movies etc. Creative PCI Express Sound Blaster X-Fi™ Xtreme Audio Hauppauge® WinTV-HVR-1200 Hybrid Analog/Digital TV Tuner 1 GB NVIDIA® GeForce® GT420 as default video card. Thank You.