How to Format Window 7 ?

does the custom install windows 7 make all the virus, data , apps , software , files erase from my pc ?

There you are if that is want you want.:)

And if you want to clean the drive during Windows Installation:

at the first installer screen press shift + F10 to take you to command prompt where you can run diskpart commands
diskpart>enter (to enter diskpart)
list disk>enter (list all connected HDDs)
select disk 0>enter (assuming disk 0 is the desired disk)
clean all>enter (which will erase entire disk including partitions)
create partition primary>enter (which will make one new primary partition the size of the disk or you can specify size ie size=xxx)
format fs=ntfs>enter (which will format the partition with ntfs structure)
active>enter (to mark partition active so boot files can be placed on it)
exit>enter (exit diskpart)
exit>enter (exit command prompt)

You can also follow this tut SSD / HDD : Optimize for Windows Reinstallation