2 OS on one PC.How can I do it without using virtual machine?

Yes it is possible. Just use a boot loader such as GRUB or LILO. You can normally just install a flavor of linux and it will take over as your boot loader. Wiki GRUB.

Yes its possible,

If you have a windows cd or xp.. or install dvd of vista, just put it in and choose the 2nd hard drive..

After that maybe he wont recognize the second OS so you need to fix the master boot record (MBR)

just google fix mbr dual boot it will work.

Is it possible to install one more OS on my PC on second hdd or on the first one but second volume?

yes to both

try looking at these articles.

I just googled "multi boot windows 7 linux"

people dual-boot all the time. the trick sometimes is the order in which you install the OS's, especially with windows. this is not something I have attempted, but others have already done it, so I refer you to their articles.

there is not any formally launched OSX version that runs on desktops. There R bit torrents and different decrease up pgms that create a digital OSX on a computer. yet desktops dont run complete OSX Apple application no count what ppl declare.

YOU SHOULD USE TWO DRIVES FOR SEPARATE OPERATING SYSTEMS AND CHOSE ON BOOT TIME TO WHICH OP. SYSTEM TO SWITCH ON.