Where did you get Win7? If you burned DVD yourself, try burning another using ImgBurna at 4x speed.
Do you have the latest BIOS version update? If so, try resetting the CMOS: Clear CMOS - 3 Ways to Clear the CMOS - Reset BIOS
What is the SATA controller setting in BIOS setup? Try AHCI first, then IDE mode if necessary.
Try wiping the HD before install: SSD / HDD : Optimize for Windows Reinstallation
Then test your HD using maker's diag/repair full CD scan: Hard Drive Diagnostics Tools and Utilities (Storage) - TACKtech Corp.
Try removing all but 2gb of RAM to try install. Then test your RAM using memtest86 CD for 5-6 passes.