Although there would be a performance difference, I doubt it would be noticeable. Especially if your motherboard and current hard drive use ATA133. I say this because SATA hard drives transfer data at 150MBps, and IDE(PATA) hard drives that use ATA133 transfer data at 133MBps.
As you can see, 133 and 150 arent that far from each other, and therefore have a very very small performance difference. Not to mention, a hard drive cant even have a sustained data transfer rate of 133 let alone 150. The high interface speeds are there for (as algu said) burst rates.
I dont recommend getting a SATA to replace a PATA drive just because it will perform better, because you will be disappointed in the difference, or lack thereof.
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