I can't help with locating another disc, sorry.
I do have a couple of suggestions and questions though.
1. Is current PC installation OK, or do you need to re-install it right now?
2. Do you have any hard drive image clones or restore points if current install corrupt?
3. What is current OS - XP vista, Win 8 etc?
4.What is the extent of disc damage?
Is it readable, but just won't install?
READ THIS FIRST:
http://www.trade2win.com/boards/first-steps/180578-old-versions.html#post2213730
As a last ditch attempt at disc recovery, you could try polishing scratches out -
http://electronics.howstuffworks.com/repair-scratched-cd.htm
http://www.wikihow.com/Fix-a-Scratched-CD
As a last ditch attempt - I've repaired discs using brasso or T- cut,
rub from centre out - never circular motion.
Suggestions:
1. If current install OK - buy
Symantec System Recovery - Available to buy online as download.
Then create a backup image of your whole PC installation.
This is very handy anyway, even without the problem you've got.
2. Current install not OK - still create an image clone as above.
Then you can either try repairing it (install windows over top without format)
or use a restore point if you have one.
If the first attempt at OS installation repair fails, restore the image clone and try something else.
Some more details of the exact problem will enable me to give more
specific advice.