Recommended test for bootable windows

[Loving, Kent]

For a dual boot (winXP + Linux) system I want to normally boot the windows. But 
there will be times when the windows partition is not yet installed. In this 
condition it's best if grub boots the Linux instead of wasting boot to windows. 
I suppose I could check for the presence of an important file, like NTLDR. Is 
the a better way?

Second, if the windows is present but in some corrupted and doesn't boot, I 
want grub to boot the Linux on the next boot. So is there a good way to test 
for a failed boot attempt?