The STO installation DVD is a double layer DVD (which are uncommon in the industry) It could very well be your device can read single layer DVD media fine, but flakes out with Double Layer Media... You may have to ask around and see if you can borrow an external DVD reader you can plug into your computer... Otherwise, the download of the Client software would be your last resort...
Comments
1: Try to use a drive cleaning disk
2: Get a new drive.
Your drive is probably past it's lifetime, OR your're still using a regular CD drive rather than a DVD drive. In any case you need a new.
It is the typical indication that a drive is dying... First it cannot read one disk, then two and BOOM... suddenly it can't read nothing anymore.
disk not work on the disc drive i atatcked to it so ill trie the Client