Current supported versions are Mint 9 LTS, Mint 11, Mint 12, and Mint 13 LTS.
Mint 11 is supported until October 2012, and will give you the same desktop experience as Mint 10, plus some breathing room before it's support runs out.
Mint 13 with MATE is meant to be a continuation of the deprecated GNOME 2 project, with the editable panels and customization options many know and love. Mint 13 with Cinnamon is designed to offer the traditional desktop paradigm while taking advantage of the technological improvements GNOME 3 has to offer.
Moving away from Mint, other GNOME 2 choices to consider would be Debian 6, Solus OS, and Fuduntu.
GIGABYTE GA-P35-DS3L LGA 775, Xeon 3.0 Ghz Core 2 Duo, 4 GB DDR2-800, EVGA 8800GT, WD Caviar 250 GB SATA-2
Ubuntu 12.04 LTS, Crunchbang Waldorf, Mint 13 w/Cinnamon, Elementary Luna Beta, Puppy