Is this a Hard Drive problem?

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MB - Gigabyte DS3, HD - Seagata 320Gb SataII

Okay so sometimes (more often than not) my computer wont get into windows (hd has xp on it).

Firstly it stays on the gigabyte ds3 splash screen for a while, then it either gives a system disk error or an error reading disk message. While this is happening the hard drive light stays on permanantly.
Sometimes though it gets into windows fine but can have problems hanging on the 'saving settings' screen when shutting down.

With the problem I have noticed that the drive isnt seen in the bios.

Windows has run the chkdsk programme and automatically amending some files and i have run seatools quick test and it picked up no errors.

Any ideas?
Is this a motherboard port problem or a hard drive problem?

One thing to note, I have a 74gb raptor with Vista on it and when i boot into it i can clearly see the 320gb hard drive there with all files on it...

 

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ive tried it on the yellow and purple ports, both eventually get the same problem.
my raptor seems to be recognised at every start up and is running vista fine so im assuming there must be some bad sectors on the hard drive.
think i will buy a new one today and see how it goes.