DVD player on my computer

This will be a problem with either the DVD decoding software, or the DVD reader inside the DVD drive. It's common for a CD/DVD combo drive to have the DVD end go out. If you have access to an external DVD drive connect it and see if it plays DVD's. If it does, then it's the DVD drive, if it doesn't, then it's a software issue. If you don't have access to an external, you can try uninstalling and reloading the decoding software or try different decoding software. You should be able to find software at filehippo.com, don't worry about it being burning software, in order to burn it has to decode first.