Inspiron 17R 5720 will not boot (Hard Disk)

Recently, my laptop stopped booting.  It started with identifying corrupt system files (associated with AVG Anti-Virus software) which I was able to remove, but did not make any progress.

I did the pre-boot diagnostics and get the following:

• Error Code  2000-0142
• Validation 1-5170
• Msg:  Hard Drive 0 - S/N S2WZJ90C813623, Short self test unsuccessful.

I did a chkdsk /r and it did seem to resolve a lot of issues, but still no luck in rebooting.  I have connected an external HD and have been able to XCOPY a lot of the user files off, so that is good.

Also, my system is long out of warranty.

So, a couple of questions:

1. Anything else I should consider before replacing the HD?  
2. How do I determine a compatible HD?
3. Right now, I don't believe I have a system restore disk or installation media (still looking), so what are my options to reload?

Thanks in advance.