You can reach BIOS, therefore you can make CDROM/DVD to be 1st boot device even if you cannot get USB drive to be recognized. Using another good computer, download and make a fresh installation copy of Windows 7 on a new CD. Adjust boot order and try to boot from the new media - and to use 'repair' if possible as you may then be able to copy your personal data from a 'fixed' HDD.
The point is that the system should recognize and boot from the HDD, the CDROM and the USB Flash Drive - every one of them should work. If they don't, it is most likely that the tracks you are trying to boot from are corrupted - so in each case it is best to try new media - especially, CDROM (a second copy is cheap; proving it works on another machine is easy) and USB Flash (proving it works in another machine is easy).
To take troubleshooting beyond this point requires detailed information, careful observation, clear description. Alternatively, you may wish to take to repair shop at this point. Otherwise, please describe steps as you take them and results that you experience.