Ntldr is missing xp fix

If the "real" ntldr file were missing, you would not be able to startup Windows. It is a hidden file in c: \ (root directory) and does not have .exe file extension - So the quaranteed files by AVG were probably picked up as infections correctly. Right click "My Computer" > Click Manage, then disk management.....Anything look out of place for the drives ?

Just download a copy of ntldr from the web (from a reliable source!) or copy it from your installation disk, and paste it to your C:\ drive.
(Open the C: drive and just paste it in.)
I just did this a few weeks ago and it worked great.

Just noticed that you're talking about something called "ntldr.exe".
This sounds like malware blocking your drives from opening.
Stat in safe mode with networking, download and run Superantispyware and Malwarebytes if possible, delete what they find and that should handle it.
If that doesn't work, go to bleepingcomputer.com and see about running Combofix (but read the warnings and directions first!).
You may have to d/l these apps on another computer and then run them from a flash drive on your computer.
Good Luck!

Thank you for both your replies, sunsmasher and ksiemb.
I guess AVG did get it right, My Advanced sytem Care downloaded a whole host of updates from Microsoft and I have not had the problem since. I cant honestly say how I got in that situation in the first place, but was extremely pleased to get your suggestions as both helped me for the future when things go wrong like that.