Hi welcome to seven forums (if you havent been welcomed yet)
Now, this may be a dumb question, but did you format and start a clean install?
- if not, insert your windows 7 cd in the dvd rom, restart pc and go into your bios (usually pressing "delete" at startup gets you in the bios) go to boot options and select your dvd/cd rom as primary boot device. press f10 to save and exit. When asked to press any key to boot from cd do it, and follow instructions, make sure to do a clean format on your selected hdd and reinstall windows. After this and windows booted up,you can install you new motherboard drivers along with any other drivers you need.
When done with all the drivers restart and go into bios again and select the hdd as the primary boot device.
If you have done a clean format in the very beginning after you installed the new mb and cpu, check that your hdd settings in bios is IDE.
Hope this helps.