My brother kept telling me that has computer was running slower than it normally ran. It also wouldn't burn DVD's. After reading the DVD burning log, I thought that the problem might be the hard drive. So, I downloaded HDTach and it showed that the burst speed and average throughput was only 3.3MB/s. Any help would be much appreciated.
Go into your device manager under "IDE ATA/ATAPI controllers".
Right click on "primary IDE channel" and select properties. On the advanced tab, make sure it's set to "auto detection" and "DMA if available". You should also be able to see the current mode it's running in.
It may not be totally fair to place the blame on your brother for windows going back to PIO mode.
If the hard drive is faulty and sends to many errors, windows can 'automatically' drop the system back down to PIO mode for increased compatibility, or if IDE a cheap cable, or using the wrong type 40 wire instead of 80 can cause similar problems.
Another source of blame is a fairly 'common' anti piracy program called 'StarForce' its a load of ......, and one of its more common side effects is to slow down disk I/O to such a degree that windows believes the drive is having errors, at which point windows drops back to PIO mode again.
As you found out, uninstalling the Primary/Secondary controllers allows windows to redetect the drive and revert to UDMA mode, but if its a bad disk/cable/starforce installed, its could well revert to DMA mode at anytime, without any warning.
Windows being windoes, its even possible that it was just the wrong time of month, the moon was in orbit or satern, mars was in assension, while uranus was in decent, and a black hole was passing through the solar system at 90 degrees.