GPT, MBR, AHCI Win7: alphabet soup

[videobruce]

My situation;
1. Existing 1 TB HDD; partitioned 10GB w/XP, 600 GB for media, 300GB for program, photo & document storage.
2. Increase the 1st partition to 20-25GB from the 2nd partition (resize both & merge),
3. Load Win7 64 bit in the first, replacing XP.
4. Retain the 2nd & 3rd partitions without loosing data (it is backed up elsewhere).
5. Save a image of 'C' to install a mirror O/S on a SSD.
6. Using a MB with a UEFI BIOS set to AHCI.

Questions; I know the hidden partition is MBR, but, when & where does the choice of MBR vs GPT happen? I've loaded Win7 on a small SSD, but I didn't see any choices.

I know I can just wipe the existing drive, but I would prefer not to unless absolutely necessary. If for nothing else, gaining the experience of doing all of this.

The more I have read, the more confusion this seems to be. I had less trouble 13 years ago with Win98 on my first PC build.

 

[petteyg359]

MBR has a maximum disk size of 2 TB. GPT is, for all practical purposes, unlimited. Even if your disk is smaller than 2 TB, GPT may be desirable because it creates a backup copy of the partition table. If you're prone to accidentally starting a "format c:" or the much harder to accidentally trigger "dd if=/dev/null of=/dev/sda bs=512 count=1", that backup copy could be useful. I don't think XP is capable of using GPT disks at all, though. If the disk is not pre-formatted in GPT, or if it is smaller than 2 TB, I don't think Windows 7 will even ask about using anything but MBR. GPT shouldn't be necessary for UEFI to work, AFAIK.

 

[RGone]

2. Increase the 1st partition to 20-25GB from the 2nd partition (resize both & merge),
3. Load Win7 64 bit in the first, replacing XP.

IF you installed Win7 into the first partition C: as you seem to indicate, then there is no hidden 100MB partition. That hidden partition is made if Win 7 is not installed to a redi-made partition. Therefore the Recovery Data is stored in C: generally.