How can I recope my hard disk total space in clean install

Hello chaps, I have for a friend of mine who has got a brand-new Lenovo laptop with Windows 8 and he has come to me to format and install windows 7 into that. Now I have done all the boot sequence and stuff and came on the fresh install screen and then deleted all the unnecessary partitions that his laptop had. The problem I'm stuck with is that his total hard drive is 750gb but after deleting 6 unwanted partitions it's now showing me 692gb only in 1 disk. How can I recover the remaining 50gb hard drive. I'm now on the disk part menu doing a clean all command to ensure a zero base to install. Problem is to find the 50gb hidden hard drive space, how can I do that please

Thanks

A 750 GB hard drive will not show as 750 in Windows.

More like in the 690 to 700 range. There's a roughly 7 percent loss. Turns out there are 2 ways of measuring capacity. Windows uses one. The disk makers use the other--the one that flatters them--as you might expect.

If you are doing a "clean all", let it complete, do a base Windows install, and then post back here with a screen shot of Windows Disk Management.

692 GB available on a drive advertised as 750 GB is about right. The difference is caused by the differing definitions of what 1 GB means. Most drive manufacturers define 1 GB as 1,000,000,000 bytes while in Windows it is 1024 x 1024 x 1024 or 1073741824 bytes. Do the math and that comes to about 698 GB. That apparent 50 GB lost never existed and there is nothing to be regained.