One of them is that your CD drive doesn't have the region set correctly, and it conflicts with the regional setting on the installation disk. It's worth checking this before trying other, more exotic solutions.
1. Right click on the drive in My Computer,
select properties, hardware, then click on the drive, properties and finally
2. If the region is unspecified, selecting the appropriate one for your area may solve the problem.
Try it, and if it doesn't work, come back to your thread and we'll try something else.