Q: i have downloaded yosemite if i update the software im unable to do that . its showing me osx could not be installed on your computer . a mismatch between the MBR and GPT partition maps is not supported with this operation.quit the installer

are you trying to install to an internal or external drive?

The first thing you should do is backup whats on your computer now before proceeding with any attempt to install this.

If there is a mismatch on the master boot record you may need to reformat the drive to install Yosemite.

Again, don't do anything before you backup.

the simplest way to back up your HD is to get an external hard drive or USB flash drive large enough to fit it all, I'd go with external HD and use Apples built in Time Machine software to manage the backup. Connect the drive to the mac and the OS will actually trigger Time Machine to ask you if you want to backup to it. You don't need to do anything else. You don't want to back up to your boot internal drive or partition on that drive; if the drive has issues your backup can be compromised.

read the reviews and find a reliable brand: IMHO Seagate is the brand for price and reliability and I've had the least amount of problems with them on dozens of macs and PCs. A 1TB HD is going to cost between $50 and $75 mail order, expect to pay $150 - $250 for 4 to 5 TB and it's possibly the smartest investment you can make in the event your internal drive crashes or you accidentally delete something vital and in lieu of spend $100 on restoration software and crossing your fingers you have a backup right there.

are you able to DL an ISO image instead of the .EXE or do you have someones PC you can use?

wow, my bad, I was answering another question about bootcamp that did not apply to you.

you still need the backup or it's in your best interest.

I'm reading more about this here but don't pull the trigger on any of this until you get some more feedback from someone who may know what the exact outcome is going to be

http://forums.macrumors.com/showthread.php?t=1872141

I think it's in your best interest to wait until someone else either weighs in on you formatting your HD and wiping it clean or not since it's a one way street once you do it.

I don't use Parralle's, if I use windows on my Mac I need all cylinders firing and all the RAM I can get, a virtualized session will run windows but it will share all the systems power between mac OS and itself, but I do mostly 3D work so thats very CPU and RAM sensitive.

JimmyCMPIT

A+, N+, MSCE, not just on paper, I have a real job that lets me drink coffee all day and mess around in Blender and Creative Cloud when nothing I support is bursting into flames, mostly what I support are a room full of mac users and the occasional Windows server. I'm also a fairly-smokin' lead geetar player IMHO.