Also, please make sure that your system will support a 64-bit OS. If it will not, drivers will likely not function properly on your system after the install. If it will only support x86 you will likely have driver issues so make sure you know your system.
To upgrade you have to do a custom install. Back up EVERYTHING you do not want to lose in case a format is needed. I used the same method to upgrade from xp back in November of '09.