The hard drive is the first point of failure I would expect.  How did it fail? Do any lights turn on?  Does it make any clicking or scraping/scratching sounds?  Does it post a boot screen or a failure code or just a blank screen?

Without more information, the easiest choice is buy a new DVR and swap it out.

Do you want another 8 camera system or do you want more/less camera support?
Do you want a higher resolution system?  If so you'll end up needing to replace your cameras too.
Are your current cameras analog or digital?  Analog taps out around 720p, but you won't have to replace all your cabling if that is what you're already wired for.  960H is the format name.
Digital system will get higher resolution, cost more, require you to replace your analog lines with ethernet cabling.

When my old analog system died I replaced it with a 960H dvr and cameras because I didn't want to crawl around in the attic over again and run ethernet cabling.  The resolution difference from cheap ~400TVL to ~800TVL cameras was a big difference.

I ended up with basically this 16ch Qsee DVR but different cameras, bought separately, for < $400 all off amazon.
https://www.amazon.com/gp/product/B00IKR21W0/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
Been happy with it so far.  The bullet cameras with built in IR all have the issue that spiders will build their web right over the camera if you don't provide alternate IR sources.

Menu inaccessible seems like the DVR itself.  If hard drive fails in DVR most systems will still boot and operate but it will beep and a notice will appear about hard drive failure.  Cameras and stuff would still work but nothing would record.  Do you keep it an enclosed place with poor ventilation?  If you're technical you can open up the case and start checking for bad solder joints and check that all the fans are still working (repair/replace as necessary), clean out all the dust, can even take the hard drive out and plug it in to a computer to check for hard drive errors.  May go back to working after that.

If you're not technical and just want a replacement, look for the cheapest standalone 8ch DVR of the appropriate hdd size.  The price difference from a standard definition analog system to a 960H analog DVR is minor, so I'd steer you towards that, so in the future you could buy better analog cameras and reuse your cabling.  One thing to look out for is on the different DVR models that support 960H they don't all support 30 frames per second.  Plenty will give you 24 or 15 or 12 frames per second.  

For example this one does CIF at 30fps but 960H at 12fps:  (CIF is what your current cameras most likely are)
https://www.amazon.com/Zmodo-Channel-H-264-Security-ZMD-DX-SBL8-500GB/dp/B01H0YQ06G/ref=sr_1_4?ie=UTF8&qid=1471990346&sr=8-4&keywords=dvr+960h (not an endorsement, but shows you the ballpark of low price, I have used this company before, very engrish)

To get above bargain chinese product you'll need to spend more money.  All up to you.  Good luck.