Finally... after tons of reinstallations and retries, I finally managed to create a new user-account which did work with gksudo and didn't get any "username not in sudoers file" message. Thank you to everyone, including Clem, in the irc channel who helped me so much!
Now, on to the topic of booting with my 2 hdds, I'm completely stumped! I've edited fstab and even tried booting Mint with only 1 of the other 2 hdds connected but Mint refuses to boot! It'll only boot IF my 80 gb hdd is the only hdd connected to the system. Yes! Mint won't even go past "booting..." if any of the other 2 hdds are connected.
I loaded Testdisk from SystemRescueCd and it doesn't seem to detect any superblock errors with my other 2 hdds, or with my main linux partitions(/ and /home). Any suggestions before I give up on this very thorny issue? It seems that either GG or this variant of GG is much more trouble than is warranted. I'm thinking I should stick with either FF or an older version of Mint before I go out of my mind.
Edit: If I boot into Recovery mode with my 160 gb pata hdd, Mint boots halfway and stops at the "uniform cd-rom driver revision blah blah" line. I'll try it with my other 80 gb hdd now.
Also, even if I toggle acpi(acpi=off), it doesn't work either.
# /etc/fstab: static file system information.
# <file system> <mount point> <type> <options> <dump> <pass>
proc /proc proc defaults 0 0
UUID=0afca1f8-618b-4972-a02e-e3bf5a17fe45 / ext3 defaults,errors=remount-ro 0 1
UUID=c46971c0-dc7f-4447-9a8a-0f79eae92242 /home ext3 defaults 0 2
UUID=56B4D57FB4D56253 /media/sda1 ntfs defaults,umask=007,gid=46 0 1
UUID=bb018198-3831-4217-89b1-ee6058c401cf none swap sw 0 0
# Entry for /dev/sdc1 :
UUID=04188596-bf72-4175-a32e-66788620fabb /media/sdc1 ext3 defaults 0 1
UUID=736cd583-c35f-45e2-b288-40af01fcc8ad ext3 defaults 0 2
# /dev/sdb2 /media/sdb2
UUID=792c6c42-9186-4e8c-abaa-270b8a600d2c ext3 defaults 0 2
/dev/sdd1 /media/sdd1 ext3 defaults 0 2
/dev/sdd2 /media/sdd2 ext3 defaults 0 2
/dev/scd0 /media/cdrom0 udf,iso9660 user,noauto,exec 0 0