Description of problem: If you choose to install Linux on a fresh computer, you can only setup GPT tables, MBR is not an option any more. Please give the user the possibility to choose a MBR layout. Version-Release number of selected component (if applicable): Fedora 16 alpha
MSDOS labels are obsolete. Larger drives need to be able to address more space and GPT provides this. For BIOS systems we install a small BIOS boot partition for grub2 to use when bootstrapping the system so there should not be any issues. If you have an actual problem booting a GPT labeled install on your system please open a bug with the logs and system details.
You cannot use Windows 7/32 bit anymore (on the same disk): http://support.microsoft.com/kb/946557/en-us Nevertheless, most people are familiar with the old mpt tools, also some recovery disks. Why not give the user the option to choose the way he like?
Most users do not want to be bothered with such technical details, and those who do should be capable of creating their own disklabel in advance of the install. All you have to do to prevent anaconda from creating a new disklabel is have one there to begin with and choose any partitioning option other than "Use All Apace" or "clearpart --all".