BIOS also updated to latest version.
Test on another PC with same Black Caviar drive and OS with similar speed results.
As I noted before, this is an older drive. Even though it is a Caviar Black, the numbers aren't going to be anything to write home about compared to current drives. While your numbers do look a LITTLE low, they're not ridiculously low. Even if you got the maximum performance this drive is theoretically capable of, you would probably notice little or no difference in actual usage.
Can you expand on the misaligned suggestion ?
On many newer drives the native sector size is 4K instead of 512 bytes; this is referred to as "Advanced Format". If you have an Advanced Format drive and your partitions aren't aligned on 4K boundaries you can take a substantial performance hit, especially on writes.
I'm pretty sure this is NOT your problem, because A) the drive is old enough that it is almost certainly NOT an Advanced Format drive; and B) Windows 7 should take care of the 4K sector alignment automatically.
BTW. HD Tune screwed up my W7 boot on the second PC. Good job I had a recent image to recover to. No more HD Tune !
If you use HD Tune Pro
(paid version) and enable write tests, it writes to the raw drive (ignoring your partitions and file system). This is necessary to get accurate results. A warning pops up to let you know that it will destroy data.
If you WEREN'T using HD Tune Pro (i.e. you were using the free version), then HD Tune wasn't the reason your drive got screwed up.