Will this HD fit my computer?

As a general rule of thumb, be careful with new Seagate drives - after acquiring Maxtor, they dropped their more expensive manufacturing processes and adopted the cheaper Maxtor processes, which has lead to a massive decrease in quality. The entire range of 1.5TB drives is faulty because of the change in manufacturing processes.

Saying that, my terrabyte drive is OK, as are my two 250s (and my two 160s, but they're three years old), and all of them are Barracuda's.