Check for a firmware upgrade for your DVD drive, most manufacturers have updates and utilities, these often resolve read issues with DVDs.
Re: vista and uninstall/re-install.
Installs are tracked in 2 places, registry and an installation tracking directory under c:\program files\common\
There was a utility that will clear out this stuff but has been discontinued by MS, MSICUU2.exe, and you may be able to get a copy from the web - use at own risk!
A regcleaner will fix the registry aspect, and I would recomend that course..
A search of the hard drive for files containing the product name may reveal the installer DB location, moving any files found to a safe location may re-enable a re-install.
You should NEVER manually remove a program, always use the uninstall utility to prevent these issues!