Conversion Factor...

Normally if you purchase a PC with 80Gb hard disc and after installing Windows or other OS in it you can find out tat in system propeties tat the whole hard disc size is not 80Gb BUT just near 74.4Gb approx...There s nothin to blame or curse the shopkeeper for tis...Because the hardware components are measured as 1024bytes per Kb,1024Kb per Mb & so on...But the Os shows u in terms of 1000bytes per Kb,1000Kb per Mb & so on...Therfore 80Gb is 80*1024*1024*1024*8=687194767360 in terms of hardware &
80*1000*1000*1000*8=640000000000 in terms of Os...
So,the conversion factor for calculating your systems original space in OS is

Hard disc memory*1000*1000*1000/1024*1024*1024=Hard disc memory*0.931322574615478515625

So for example 80Gb*0.931322574615478515625=74.5Gb approx...

Try it out for ur system....