Dunno if this has been said yet but when your computer is booting up, enter bios, set boot device to cd drive, put in windows disc, and boot from that, install windows on different partition, boot from that partition, find the DLL you're missing, copy it onto a thumb drive, note the location of it, boot windows in safe mode, paste dll into other windows folder, set the boot partition to old windows and then it should work.
Or just format and install a fresh copy of windows if you're lazy