external HD dying, or config problem? VERY slow transfers

I have a 750GB external hard drive with both USB 2.0 and eSATA interfaces. The drive itself is WD (WD7500AAKS) and the enclosure is made by "Cavalry" (came with the drive pre-installed).

Benchmarking results using HD Tune suggest that all is well. Using the eSATA interface, HD Tune shows 77MB/s average, 99MB/s burst, and 13ms access time, all of which seem great to me. However, when attempting real-world file transfers, the rates are absurdly slow (on the order of 1.5MB/s).

For instance, I did a test transfer of 9.13 GB (approx. 1,500 files) and had to cancel after passing the 60 minute mark (hadn't even made it through 4GB in that time).

The USB 2.0 interface has the same problem.

I have tried transferring from two different internal drives -- one SATA and one PATA, and the real-world transfer speeds continue to bog at unusable speeds of around 1.5MB/s. Both internal drives also test healthy in HD Tune.

As an extra test, I tried transferring about 7GB of files from the same internal drives to an 8GB flash drive (Class 6 SDHC, through USB 2.0), and things were as speedy as one could hope for (over 15MB/s). Transfers from internal drive to internal drive are also fast.

What's going on here? Why do the HD Tune results look so good for the external drive while the real-world attempts fall flat? CPU usage during transfers is very low (under 5%) and I checked the Task Manager to confirm that no programs were hogging memory.

The drive came pre-formatted NTFS. I tried reformatting the whole drive on the chance that something went awry in the initial formatting, but no dice -- results were unchanged.

The system is running Windows XP. The main internal drive is a WD 7200 RPM SATA drive.

Any suggestions for additional troubleshooting steps?

What I'd like to do is take the external drive out of the enclosure and hook it up internally to test transfer speeds, but doing so will invalidate the warranty (which is still valid), so I can't do that yet.

Thanks in advance for any thoughts.

i could be wrong but isn't the standard test in hd tune only how fast can the hd read? instead of actually transferring files? i think that's it's only read. hmm then again i think that the pro version has write feature. which one are you using? also try different programs to test your hd, like hd tach