The Disc and the Product Key where you can do a In Place Install by following the directions here
http://support.microsoft.com/kb/315341
Follow the directions listed under Method 2 to perform the install.
But it will not make the old Apps work and I'm frankly surprised that they still remain on the HDD as HP generally does a Format which is Destructive [i]well to your data and installed software at least[/i] and then proceeds to install the OS and associated software on a clean Partition so that there are no previous files/directories or so on to cause any problems.
As for getting the Software to work again you'll need to install it all again as the Roots within Windows have been deleted and these need to be rebuilt before most Windows Software can run.
So at the very least you'll need the M$ Branded Install Disc and Install Disc's for your Installed software things like Office and so on and whatever Install Files that are required for any Utilities that may have been installed. Things like AVG Free and Malwarebytes should be included as a bare minimum if you don't already have some kind of AV product to install.
http://free.avg.com/download-avg-anti-virus-free-edition
http://download.cnet.com/Malwarebytes-Anti-Malware/3000-8022_4-10804572.html?tag=mncol&cdlPid=10878968
Col