Its really wierd...
It wont accept that or any of the other suggestions, the only way I could get the HS_OSC in the code so it produced no errors was to use DEFINE pic16F877a,HS_OSC
However, although this gives no errors when you compile it, when you try and program it using Picflash it still sets Oscillator to XT and not HS
guess i'll just have to keep an eye on it and change it whenever I program it