Do NOT worry about HDD's over 137 GB. ALL SATA drives and controllers have 48-bit LBA Support included.
foscooter pointed out your mobo MIGHT have only the first version of SATA controllers, but if it was bought in 2007 or '08, you are more likely to have SATA II (i.e., 3.0 Gb/s communication speed). So SATA II drive are fine for you. With standard mechanical HDD's there is NO advantage to SATA 6.0 Gb/s, because no mechanical drive can even get up to the previous SATA 3.0 Gb/s speed. SATA 6.0 is useful now only for SSD units - solid state, VERY fast, VERY expensive per GB.
thanks for all the help guys and that link did die the night I posted it like right after haha. But I bought a 1.5TB instead of 2 because it was a lot cheaper. Hopefully that fixes my computers problem.