You could try that one but there's no guarantee it will work. Apple's system DVDs (it's a DVd not a CD) are often machine model specific nad there are many sub models of MBP.
Here's older posts but maybe they still apply:
Mac OS X 10.6 Help: If you forget your administrator password - http://docs.info.apple.com/article.html?path=Mac/10.6/en/11627.html
Reset OS X Password Without an OS X CD - http://theappleblog.com/2008/06/22/reset-os-x-password-without-an-os-x-cd/
rccharles post on editing password with single user mode - http://discussions.apple.com/thread.jspa?threadID=2747898
Regaining lost admin status on OS X - http://www.salingfamily.net/trav/osx/regain_admin.html
Running OS X Setup Assistant (another topic) - http://discussions.apple.com/message.jspa?messageID=9581230
If it really is a MacBook, your wife's MacBook Pro DVD is not likely to work.
Insert the disc and start the MacBook while holding the C key. If it does not start from the disc, and goes right to the login screen as you have been seeing, or gives you a message to the effect "this disc cannot be used on this Mac" then try the links Limnos provided.
An underlying concern is whether the MacBook was legitimately sold, and not stolen. Sellers should always include the system installation discs, and buyers should always insist upon having them. No exceptions! The ability to troubleshoot and correct potential problems will be hindered without a system installation DVD.
You could try contacting Apple to see if you can talk them into selling you a replacement system installation DVD. They will need the Mac's serial number and some cash.
New Macbook Pros do not come with install disks, even new in the box as far as I can tell from reading the info at the Apple Store.
I'm looking at a used unit on eBay and have concerns about what to do when it arrives. It will have Mountain or Mountain Lion on it, but it will have the other person's ID attached to it I assume. Would I want to erase the eBay MBP's drive and install a new OS, perhaps downloaded from the App Store? Just wondering the procedure in a case like that.
If the Mac shipped from Apple with Lion or Mountain Lion already installed (approximate build date of August 2011, there will be no discs nor will you require any to reinstall Lion or Mountain Lion.
If the Mac shipped with installation discs - in other words Snow Leopard or earlier OS was installed when it was built, then it must be always accompanied by those discs.
A Mac's original OS may always be reinstalled for free. This has always been the case. Problems arise when sellers install a superseding OS version and do not include the original OS version on disc. Beginning with Lion, such discs are no longer necessary. Mac OS X licenses purchased from the App Store (at present, Lion and Mountain Lion) may not be transferred.