XP Pro SP3 Bluescreens - kernel & atapi.sys errors

This system has been running great for a few years, all of a sudden last week it started getting bluescreens and restarting all the time. Details are below, most of the errors and event viewer messages seem to be disk related.

I opened up the machine, cleaned up dust, reseated RAM chips and re-attached HDD cables. Also ran chkdsk /r /f.
Everything was good for a few days.... maybe because it had been powered off for a while? but today the same problems started again.

I have no malware or viruses. Also checked the temperature with CoreTemp, and I see nothing unusual.

Where is the problem? Do I just need to replace the hard drive? Or is it something more serious?
I can replace the hard drive and reinstall the OS but question is if it will start happening again.....



System information:

- Intel Core 2 Duo E7300 @ 2.4GHz
- Gigabyte GA-EP35-D53L motherboard
- 2 GB RAM
- 250 GB Western Digital SATA HDD WD2500AAKS (2 NTFS partitions)
- Windows XP Professional 32bit service pack 3


Examples of bluescreens:

- STOP: 0x000000F4 (0x00000003,0x8A42D480,0x8A42D624,0x8050299C)

- KERNEL_DATA_INPAGE_ERROR
STOP: 0x0000007A (0xC05BF8C0,0xC000000E,0xB7F1850C,0x54D6E860)
atapi.sys - Address B7F1850C base at B7F0B000, DateStamp 4802539d

- KERNEL_DATA_INPAGE_ERROR
STOP: 0x0000007A (0xE1D75878,0xC000000E,0xBF9067CB,0x3497F860)
win32k.sys - Address BF9067CB base at BF800000, DateStamp 483fe7ff


Some errors in Event Viewer:

- Source: Disk, event ID: 7
The device, \Device\Harddisk0\D, has a bad block.

- Source: Disk, event ID: 51
An error was detected on device \Device\Harddisk0\D during a paging operation.

- Source: atapi, event ID: 9
The device, \Device\Ide\IdePort2, did not respond within the timeout period.