go into the BIOS and make the dvd/cd rom drive first boot device. make the HD 2nd.
put the W7 disc in the cd tray/shut it. hit F10 and then enter. let machine reboot. Watch the screen. soon it will ask if you want to boot to cd. say yes.... or hit enter i think it is.
let it do it's stuff. it will come to a blue screen where it will ask you to agree ( hit F8 ).......... soon you will see a screen for (R) repair......... let the one go. the second time around you will have "R" and full install. select the "R" then. let it do it's stuff. it should repair your opsys............ when the machine reboots ( and I think it does a couple of times )..... do not hit the "enter" key to boot from cd-rom....... just the first time is all you do. it will seem like a new install but it does a repair but you will have to agree to stuff and reset things. just go with it........ when you are finally done go into the BIOS and make the HD first boot device again and cd-rom second. F10/enter to reboot.
Using your windows dis try to repair the current install (the disc will boot windows and give a repair option) If you can not, you will have to do a clean install. All your programs and setting will be in a folder called old windows in the new install. However you will need to reinstall all the programs. This is because windows figures that if it can not be fixed to run correctly, the issues may be in the registry or system partition. So then these must be replaced and it becomes a clean installation.
Then you can not do what you want. You will need to do a clean install of Win7. There will be a file called "Old Windows" created during the new install. It will contain your old files, data and settings. You will still need to reinstall all programs and drivers. Also any device software (printers, scanners, cams, etc.).