You're stuck for now. Look at the PC and if it's some HP, Acer then call them and order the media.
All PCs require we have a backup and restore plan. Those that never heard of this often learn during the disaster.
If you need to get your files out read the next link.
Works on most PCs.
I installed windows 8, updating windows 7, then I installed the free upgrade to Windows Media Player.
Now Windows 8 tries to start, then goes in to repair, but fails.
I have no discs to do a re-install, how do I get it to start.