Need help dual booting

[JBLanteigne]

Ok let me explain my setup first:

 

I have 3 partitions:

 

1) Small OS X kalyway partition I started with this one to install the 2nd partition

2) Main OS X partition installed with retail dvd

3) Blank partition, I want windows 7 here.

 

After installing Kalyway I get this bootloader which is very neat, every time I turn on my computer I get to this screen and choose my main os x partition.

 

My goal: I want to install windows 7 on the 3rd partition

How I do this: I put a windows 7 dvd in my drive and try to boot from it.

 

What happens: My computer ignores the dvd and goes to the bootloader screens.

 

What I tried so far: I went in the BIOS and I disabled the AHSI something for the SATA drives. When I do this and try to boot from dvd it says:

 

"Booting from CD/DVD:" and stays on this screen forever.

 

So... I need your help.

 

Thanks.

[JBLanteigne]

I made a bootable usb installer... and I get the same thing. After selecting usb fdd in the select boot device menu, it ignores it and goes straight to my boot loader asking me which partition I want to boot on.

[vilpostus]

First of all make the dvd drive the first boot device in BIOS. Look for this option in the boot section of the BIOS. Something like "boot device priority". Set the dvd to be the first and the HDD the second. ACHI mode must be enabled to avoid "still waiting for root device" error.

 

After adjusting the BIOS (and saving applied settings ) Now it must boot from the DVD. May also note that Windows may not be willing to install to GPT disk (if you have formatted it to GPT).

 

Another thing to check is removing a "boot" flag from an OS X partition. Use ether OS X to do that, or a GPartedLive CD.

[JBLanteigne]

I already set the dvd as the first device, that wasn't my problem.

 

I tried partitioning my back up/data drive to add some space for a possible windows partition and I ended up with the GPT disk partition architecture (or something).. I did not think of this problem, but it wasn't the reason why my computer chose to ignore booting my dvd before. I was only able to boot from dvd after I physically removed the drive (with my os x partition) from the computer.

 

So now I guess the easiest way would be to instead windows on a separate drive because I'm stuck with that GPT disk unless I do a massive back up...

 

Thats for your solutions, I'll see if I can get a cheap smaller drive just for this.

[srs5694]

So now I guess the easiest way would be to instead windows on a separate drive because I'm stuck with that GPT disk unless I do a massive back up...

 

Perhaps not. Version 0.5.0 of my GPT fdisk utility can do a GPT-to-MBR conversion, but with the big caveats that it can handle only up to four partitions, and some older OSes (such as DOS) may not like the way those partitions are defined. Those partitions will all become primary MBR partitions.

 

Another option would be to use GPT fdisk or another utility called gptsync to create a hybrid MBR configuration. In this approach, the disk looks like an MBR disk to Windows and some other OSes, but OS X and most other GPT-aware OSes treat it like a GPT disk. This configuration has a lot of potential for creating problems, but it's also extremely useful in some configurations.

[JBLanteigne]

Wow thanks! that's very cool!

 

However, before using this, I have a question.

 

If I take my GPT partitionnated drive (2 partitions, a huge one with lots of data and a smaller empty one) Do I need to format it in order to convert it to with your application? Or will I lose any files? Also, I'm not very familiar with GPT and MBR, can they both be read and edit from mac and PC?

 

Thanks

[vilpostus]

I'm not very familiar with GPT and MBR, can they both be read and edit from mac and PC?

Depends on what you mean by "read and edit". If it's about accessing files and editing/reading them, then yes it is possible.

 

If it's about partition management, then an OS X can do more, then the Windows does in this case. Windows is based on MBR. OS X is based on GPT. So each of the OS'es is limited in supporting ether of the formats.

[JBLanteigne]

Oh I see...

 

The real thing is, the drive I would convert and partition to install windows 7 also has that other bigger partition with a lot of files on it. I'd need these files to be available on both OS.

[vilpostus]

I'd need these files to be available on both OS.

It's possible. Though some drivers will be needed.

[srs5694]

If I take my GPT partitionnated drive (2 partitions, a huge one with lots of data and a smaller empty one) Do I need to format it in order to convert it to with your application? Or will I lose any files?

 

The answer to both questions is "no," with the caveat that any modifications to low-level partition structures is inherently risky. A bug, a badly-timed power failure, garbage data in the original definitions, or other problems could cause data loss. For added security, use the backup function to save a backup of the current partition table to a file (stored on a USB flash disk, a floppy disk, or another computer) before you modify a partition table.

 

Also, I'm not very familiar with GPT and MBR, can they both be read and edit from mac and PC?

 

Yes, with some caveats. First, only recent versions of both OSes understand GPT. For OS X, I believe 10.4 and later can handle GPT, but 10.3 and earlier can't. For Windows it's more complex, since it depends both on the platform and the OS. Windows Vista and later can handle GPT, but with XP and some earlier versions, it depends on the CPU architecture and the firmware type (BIOS, EFI, or something else entirely). The second caveat is that Windows is designed to be bootable from GPT only on EFI-based systems. IMHO, this is a lame and short-sighted limitation, particularly in Windows 7, since GPT will soon be required to get the most out of hard disks. (MBR can't reliably handle anything over 2TB.)

 

The real thing is, the drive I would convert and partition to install windows 7 also has that other bigger partition with a lot of files on it. I'd need these files to be available on both OS.

 

Both OSes can handle MBR, and both can handle GPT for reading -- but as I said, Windows can't boot from GPT unless you've got EFI rather than a BIOS as firmware.

 

The bigger issue for cross-OS data access is the filesystem in use. FAT is still the best in this respect, although FAT has some serious limitations (on file sizes, for instance) that are an issue for some purposes (big backup files, big multimedia files, etc.). The second best choice is probably NTFS, which overcomes those FAT limitations, but read/write support is OS X is still not that great. OS X can read NTFS just fine, but writing it requires either enabling special support in OS X 10.6 (but not in 10.5), which is known to be flaky, or using a third-party driver (the commercial Paragon NTFS or the freeware NTFS-3g). Another option is to use HFS+, which would require a special HFS+ driver in Windows. Apple provides such a driver with OS X 10.6, but it's read-only. I believe there's a third-party commercial HFS+ driver for Windows, but I don't know much about it.