How to improve harddisk performance
This tweak can increase the performance of your HDD by enabling DMA, IDE 32-bit I/O and setting the interrupt-unmask flag, which improves Linux's responsiveness. The last parameter sets the IDE Block Mode to fetch 16 blocks per I/O interrupt. Depending on your drive this value may vary (have a look into the man page of hdparm).
Caution: On some hard disks these settings may corrupt the filesystem! Again, have a look into the man page of hdparm to find out if your model is affected.
On most systems the specified device is just fine, but change it when necessary (on Ubuntu it's /dev/sda).
hdparm -d1c1u1m16 /dev/hda
Successfully tested Thinkpad models
The settings above have been successfully tested on the following models:
T20, T22, T40
Please add your model if missing.