Is GUID something to do with LVM? I am not running LVM, so I am not familiar with the terminology. If it's another name for the standard partition table, you would have to remove one of the four primary partitions and replace it with an extended one instead. The extended partition can contain numerous logical volumes.
I don't know if this will be of any help, but there is a shareware product called BootIt™ Next Generation which allows you to play with the partition
table and exceed the four primary partition limit. It allows any single operating system to select which four partitions get loaded when it boots. A single operating system can only use one to four, but each OS can use a different set of primary partitions at boot time. If you wish to read further, this is their website.