It's not reading the DVD. If you burned it yourself, confirm ISO source and burn another DVD using ImgBurn at 4x speed with Verify.
If you have retail Windows 7 DVD, make sure it is clean without smudges.
Try writing the DVD or ISO to a flash stick using Ultra ISO: on File tab open ISO or DVD, on Bootable tab Write Disk Image, Format, Write. Boot under one-time BIOS boot menu listing for USB or HD's.
You may need to borrow or otherwise find another installer ISO for your version, or unlock all versions in any version installer to burn a new DVD or write to flash stick, then install your licensed version with Product Key: Unlock any version eicfg removal tool
Tips for getting a perfect reinstall based on hundreds done here: Reinstalling Windows 7