Hard Drives:
hard drive A - 80 GB: 1 partition: C (windows XP Professional OS)
hard drive B - 250 GB: 1 Partition: D (storage files)
both NTFS

goal: to shrink D partition to 170 GB and basically copy over the partition on the hard drive A to the new empty space on hard drive B. Then permanently removing hard drive A from the system while keeping the computer running normally as if nothing happened. Basically i want to get rid of hard drive A while keeping the system running normally with the OS on a different drive letter.

so far i have shrunk hard drive B without errors.
i tried just using GParted and copy/pasted the partition on drive A onto the empty space on drive B, successful.
When i disconnect drive A, and try to boot, the computer pops an error booting OS message.

i know i have to modify the MBR, so to save time researching, could someone tell me how to make the computer boot from drive B?

(i still have all the files intact on drive A)

Do yourself a favour and reinstall.

But if you really want to do it you'll have ta make an image of the drive. Copy/paste won't work.

Acronis True Image or Norton Ghost can do this. You can't just copy and paste an OS and/or programs to another drive/partition.

You can if you do a Windows install on that partition first to make it bootable. But it's a pain as you have to boot on the new partition, copy over all the files from the old partition to a temporary directory (so none are locked by Windows), boot on the old partition, copy the files from the temporary directory to the real directories on the new partition, then boot up on the new partition again and change the drive letter in the registry.

Also, some copy protection crap has files with invalid file names which can't be copied. But it doesn't seem to care whether or not those files exist and still runs the game anyway.

It is possible to do this, but you'll have to make the boot partition the first partition on the 250GB, not the second one.

Run GParted, move the 170GB partition on the 250GB to the end of the drive, leaving the 80GB of free space in the front of the drive.

Copy the 80GB partition from the old 80GB drive to the free space on the 250GB. Set that partition active. Remove the 80GB from the computer, go into the BIOS and set the 250GB as the boot drive, and restart the machine.

I'm not positive, but if I remember correctly, the start of the boot partition cannot be beyond the 127GB point on the drive.