I installed a fresh Windows 7 overwriting Fedora 17. The installation was successful, but the laptop is not now booting. It's showing a black screen with a blinking cursor.
you can simply repair your MBR of windows
Bootrec /FixMbr // If you have Damaged MBR
Bootrec /Fixboot // If you’r MBR is having problem or Missing.
Bootrec /Rebuild //If you’re MBR is Compressed or unable to repair
You can find the detailed process here at How to Fix/repair/Rebuild MBR in Windows 7/8
Windows should have modfied your MBR, but if it didn't you might try erasing your drive from the BIOS or from a linux LiveCD or something. Then re-install windows. Key is deleting the making your whole drive unallocated space, formatting a partition will not work because it works around existing information on the drive, like the MBR leaving it intact. Erasing a drive completely and resetting it back so it is empty should fix your problem.
Otherwise, sourcing a method to fix your MBR like @karel mentioned is definitely the way to go. There are many options out there if you search for them.