I don't know how to diagnose graphically. Hopefully someone else will add an answer addressing that.
Is the problem linux related?
Take careful note of where you see the error. If it happens before the bootloader (grub), then what you see is probably a BIOS error, not linux related. You may find the rest of the steps useful, but probably not. If it happens at grub or after, then linux is reporting the error. Continue with this guide.
Search the boot messages
I would grep through dmesg to see any disk related errors. There are far better tutorials to get you up and running with linux commands, I recommend them over the following:
dmesg prints the kernel ring buffer, which near as I've been able to figure out is all the important messages about what linux is doing. If there was a boot problem, it ought to show up here.
grep is a search utility.
Hard disks in linux these days are named "sd"+letter. Ie, my first sata disk is named sda, my second sata disk is named sdb..
The pipe character,
| creates a flow of information by pouring the output of the preceding program into the following program. (Some programs like grep use the pipe symbol internally to mean OR).
Put this together and you get:
dmesg | grep "sd[a-z]"
dmesg | grep "mount"
dmesg | grep -E "error|fail|warn"
Is there a problem post-boot?
Use fdisk and df to get printouts of your current disk situation.
Does anything look weird? Are disks or partitions missing? Mis-sized? Do these programs report any errors?