It could be the hard drive failure if you have purchased the computer for a long time. In that case, you need to replace current hard drive with new and larger one. You may want to complete replacing using some third party backup & restore software if don't want to do clean install.
If it is not the hard drive's issue, it could be software conflict between Oculus and some other programs. Did you install it on system partition? Close all other running software before starting Oculus. Or move it to another redundant partition like D drive or E drive using vrBackupper which is a free tool for backing up and restoring of Oculus Rift.