Do you wanna know if your hard drive is set to transfer data at it's maximum speed? The first thing is to make sure that your controllers are set to run in DMA Mode, If Available. Even if you have already checked this before, double check it again.
I have seen spyware and other malware change this setting over to PIO mode (which you do not want.. 'cause it severely cripples your system speed).
Here is how to check...
First Go to your device manager (Start, then run then type devmgmt.msc)
Then look for your IDE ATA/ATAPI controllers and click on the plus sign to expand it.
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Then double click on your Primary IDE Controller (also sometimes called Standard IDE Controller)
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Then, click on the Advanced Settings Tab and verify that it is set to DMA Mode, if Available. If it is set to PIO only, change it to DMA Mode if Available.