mbr and other os in alienwarex51

Hi, i have alienware x51 with uefi and gpt partition. I canconvertmbr?If so, howcan I do?I have tried manyprocedures, butI could not.

I also want toinstall another version ofwindowsbuttobootthe DVDdoes not start,I canonlyboot the dvdwindows 7home premiumthat camewith thePC.There seems to beaprotection toboot.How do Istart anotherdvdthatis not the original?

Thanks!