for this purpose any "non-branded" (I.E. Dell, HP, etc...) OS reinstallation disc will work.
Most "Branded" discs will refuse to work on other make computers.
But as stated above it must be the same version of windows
(Starter, Home-Premium, Professional, etc) as was originally
installed on the computer.
I've found that the service pack level of the disc is unimportant
and I've never had an issue "reinstalling" a 64bit version in place of a 32bit version.
Also after running the installer you'll get that message that you have "three days until automatic activation" and after that 27more days to "activate" your installation of windows.
Don't be in a rush to "Activate" until you are SURE that everything works correctly.
So long as you don't activate you have an unlimited number of "do-overs"
(even at 30day intervals if necissary)
Get your drivers installed and ALL hardware functioning before you activate.
When you DO activate I'll note that I have NEVER seen "automatic activation" actually activate automatically.
When you get the message "would you like to activate now?" and push the button to do so I've seen that work <10% of the time.
What I wind up doing 9-out-of-10 times is this:
BTW, you can pick up an OEM-System builder version of Windows7 Home premium for about $90 from Newegg.com
I know it stings to buy an OS you already have an OEM right to, but I'm a firm believer in Ohms law... (following the path of least resistance:)
And if a computer company or the OS publisher tries to screw me I have no moral obligation to resist the temptation to screw them back.
BTW, if your OS works as is another way to have a reliable backup is as also mentioned above to "clone" your existing drive.
This copies EVERYTHING, programs as well as data.
My preference is for Clonezilla, but some beginners have issues with it's minimalist user interface.
The only issue I have with clonezilla is that it will only clone to another drive of equal or larger size.
(if there is a way around this that I don't know of feel free to tell me)