will_chellam :
if you want a truly free option - use winrar (trial) to extract the files from the ISO then burn them to a CD using the windows cd writing wizard.
Personally I use nero, you can find oem versions for £5 in the uk and even new dvd burners with the premium version for less than £35.
you cant simply extract files from the ISO, you have to burn the ISO using a program, (as someone mentioned in this thread, CDBurnerXP is a great one)
@inspector, its probably incompatible because you probably downloaded the wrong bit, if your using 64 bit, and downloaded 32bit windows 7 RC, you wont be able to run it, and vice versa