Can't make RA1 a digital Input on (10 out of 20) 16F887.

[Archangel]

This is your code tweaked for a PIC16F690, and it works:

#CONFIG
    __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _BOR_OFF & _FCMEN_OFF & _IESO_OFF 
;__config _CONFIG2, _WRT_OFF & _BOR40V
#ENDCONFIG


DEFINE OSC 20

ANSEL = 0
ANSELH = 0
ADCON0 = 0
ADCON1 = 0
CM1CON0 = 0
CM2CON0 = 0
CM2CON1 = 0
CCP1CON = 0
;CCP2CON = 0
portb=0
portc=0
porta=0
TRISA = %00000010
TRISB = 0
TRISC = 0
;TRISD = 0
;TRISE = 0


Startup:
LOW PORTA.0
PAUSE 250
HIGH PORTA.0
PAUSE 250

IF PORTA.1 = 0 THEN
LOW PORTc.1
ELSE
HIGH PORTc.1
ENDIF
GOTO Startup

The registers a 690 does not have have been commented out. You will need a pull up on your input pin.
Sorry I don't have an 887 to test upon.