After clicking on format in the Windows setup, it insisted that the partition should be a GPT instead of a MBR, well it was a 1TB Harddrive I was installing it onto, why it wanted GPT I have no idea, and since it had no data on it, I deleted the partition and it converted the drive to GPT and started installing Windows 7 64bit.
All was fine until May last year when I decided to format again, well it reached the Format page and after clicking on format it said it can't install on a GPT partition and needs to convert to MBR

Last week I installed Windows 7 64bit on my backup PC and it went smooth and had no issues, the drive had an MBR and only thing different was it had an internal DVD Writer, whereas I need to use an external one.
So what option did I accidentally choose on my PC in the boot order that made it ask me to convert to GPT and next time to MBR, right now my primary drive has an MBR and I can't afford to lose data if it want's me to delete the partition to convert it back to GPT, there must be something relative to external DVD writers as internal ones have no problems.
Can anyone shine some light as to what option causes it to ask GPT or MBR on a 1TB drive where neither matters.