Hi,
You'll need to reinstall Windows 7 from a disc(s), so if you didn't create your set of Windows 7 Recovery Media as described in This HP Document - then there are Two main options.
1. You can order a replacement set of Recovery Discs using the link below - these will reinstall Windows 7, all required drivers and nearly all of the original software ( the exception often being trials of MS Office ). They will also re-create all the original partitions, including the Recovery Partition.
2. Another option you could consider is to create your own Windows 7 installation disc.
Before trying the following, make sure you can still read the 25 Character Product Activation key on your Windows COA label ( 5 blocks of 5 alpha/numeric sets ).
An example of a COA Label can be seen Here.
You can create a Windows 7 installation disc yourself using your PC - just download the correct Disc Image ( this must be the same version that originally came with your PC ) from the link below and use an application such as ImgBurn to burn the ISO correctly to a blank DVD - a guide on using ImgBurn to write an ISO to a disc is Here. These Images are clean and from a well-respected source ( Digital River ).
Windows-7 sp1-iso-official-32-bit-and-64-bit
Use the disc to perform the installation, enter the Windows activation key found on the COA Label when requested and when the installation has completed, use the 'Phone Method' detailed in the link below to activate the OS - this method supported by Microsoft and is popular with people who just want a clean installation of Windows 7 without the additional software load normally bundled with OEM installations.
http://www.kodyaz.com/articles/how-to-activate-windows-7-by-phone.aspx
Additional software and drivers can be located by entering either the full Model No. or Product No. of your PC Here.
Regards,
DP-K