Check your DMA
DMA, if on, can greatly speed up communications between your PC and its hard drive and DVD/CD drives.
The following assumes your hard drive is on the primary channel and the CD/DVD drive is on the secondary.
To check if it is on:
Right click on My Computer
Select Properties
Click on Hardware
Click on Device Manager
Double click on IDE ATA/ATAPI controllers
Double click on Primary channel
Click Advanced Settings and check it says DMA if available and is set to Ultra DMA, mode 5.
Do the same for the secondary channel -- it should be Ultra DMA, mode 2.
Don't worry if it says "Not applicable" - it means there is no device connected to that port. Thanks to Blutach