absolute brain lapse

So I have been updating some code of mine, and I went to put it on my PIC 16F877A and it isn't working. I've spent all evening tweaking and probing, and I can't get it to work. While I have been debugging things, I have started to second guess some other stuff, like when I program it, do I want it to be in HS or XT mode. I don't remember what I used to use. I have a 4MHz TTL crystal feeding into my PIC, but the datasheet seems a little unclear to me. Which would you go with for a 4MHz crystal?

Thanks a ton!
~Jason

Either should work but I'd go with XT.

Mike.