Take a look at everything generally. It could be:
- HDD failure, e.g. HDD cabling etc or actual HDD Failure.
- Data corruption with EvoX, depending on where your xbox is located it could be this. If it's close to a speaker or magnetic source etc. Or if you had some sort of power surge/brown out.
Think about your xbox's age.. how long have you had it? If you have a v1.0 or very old xbox, the HDD is likely to be the issue. Though most likely it's one of these two problems, and I'd say 9 times out of 10, it can't be fixed, given that you DIDN'T do anything. Though sometimes 'not doing anything' is enough to 'do something' that you didn't even notice you did.
If you're comfortable doing so and have the tools, open up your xbox, clean it out, and inspect all elements of it.