Where did you get Windows 7? If you burned the DVD yourself, try burning another using ImgBurn at 4x speed with Verify. Confirm the ISO is intact by checking its HASH against official Windows 7 HASH or downloading another.
Are you booting the installer to try install or running it from Vista? If you're doing one, try the other.
Make sure you have the latest BIOS update. If so, reset the CMOS:
Clear CMOS - 3 Ways To Clear the CMOS - Reset BIOS
While in BIOS, set SATA controller to AHCI first, then IDE mode if that fails.
Try removing all but 2gb of RAM then try install. Test your RAM with memtest86 overnight.