Problems With Bootcamp!! Please Help!

Hi All!

First of all i realise bootcamp has been discussed to death on these forums but alas nothing has helped!

I have burned an .iso file of Windows 7& 8 on to both USB drive and CD using Disc Utility.

I have modified boot camp's info file to show the third option in bootcamp too!

Closest i have gotten is to the Windows 8 install to which would not go further with the warning "could not load onto drive.....the selected drive has a MBR partition map......etc etc"!

I really need to have Windows on my iMac to use certain programmes and would really appreciate any straightforward help any one can give!

P.S I'm no developer nor hacker, my iMac is 4 years old so care is out of the question, also with no serial number for some reason!

I'm just lost, if anyone can help, thank you!!!