Questions about Dual-Boot and GPT partitions

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mynameisdatruth

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Jul 23, 2012
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So, currently, we're trying to dual-boot Windows 10 Technical Preview on a Toshiba laptop with Windows 8.1. We already got the partitioning set up and everything, but when trying to install, it says we can't install to a GBT partition, or something along the lines of that. Has anyone had this issue before?

We went to try to install it the same way that you do for Windows 7 and everything else, but upon setting the disk drive to the boot device, it still loaded into Windows 8. After a little Google work, I found that Secure Boot must be turned off, and that the BIOS option has to be changed from UEFI to CSM. After doing that, we could boot into the Windows 10 disk. However, when trying to install it, it says "Windows cannot be installed on this disk. The selected disk is of the GPT partition style"

We would like to fix it, and I found a way to do so on a Microsoft forum, and that's as follows:
1. Boot up to installation DVD/CD.
2. Click install but don't follow through.
3. Press SHIFT-F10 to bring up console.
4. Type "diskpart"
5. Once inside diskpart type:
-> list disk (find the one you want to convert)
-> select disk 0 (select the one you want from the list)
-> convert mbr (should take a second or two)
-> quit
6. Continue with install

But I need to know if it will format the entire hard drive, as I'd prefer not to lose the data on the primary partition. If we can do it while only formatting the partition for Windows 10, that would be fine (as that's empty already anyway). If anyone could offer any assistance with this, that would be great.
 
Solution
Sorry... I actually had an important detail from above incorrect. MBR vs. GPT assignments are done per disk, not per partition, thus yes, you will definitely need to wipe out the entire drive.
1) Unless you have a license to buy Windows 10, normally it is done as a Upgrade
2) I HIGHLY suggest if your just 'testing it' to instead install it to a VirtualBox like from Oracle https://www.virtualbox.org
This is the easiest way to just 'install and test it' without affecting the rest of your system.

Personally I been using it for a bit now on the kids, and I went and upgraded my main system to it without really any performance issues as long as you have a nearly newer system it works really well AND you ONLY have profiles / programs on C drive.
 

mynameisdatruth

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I'm not just looking to "test it out", I'm looking to install it to use on the side, while still having Windows 8 on the computer as a backup as well. I already have it done on my desktop computer, and I've really enjoyed it. Your response didn't help with my problem, since I intend to install it and already know exactly what I'm doing. Also, I don't know what you mean by your first point. I know how to dual boot it, and that's exactly what I'm looking for. You also don't have to advertise it to me, thanks
 

mynameisdatruth

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Jul 23, 2012
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But do I have to format the entire drive, or just the partition?
 
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