Hard Drive failure - What to do?

Hi

I have 2 hard drives on my PC, there both 500gb.

My hitachi hdd has the C+D drive on it and is the hdd my pc runs off.
My seagate is just a spare 500gb hdd that i havent used much of.

The problem is my hitachi hard drive is having problems and i think its going to die soon so i need to get all my operating system and stuff off of it onto my other hard drive.

If i can get the operating system and boot up files onto my other hard drive i can use that instead to run my computer. The problem is im on vista home premium which doesnt have the backup option to save everything from the system, so im not sure how im going to do it.

Can anyone tell me how i can transfer all the system files and everything on to my working hdd.

this would be a great help thanks