HI,
BTW, I just installed windows and this is a fresh installation. I can compile with P16 chips, but when I choose any P18 chips I get many errors:

Executing: "C:\PBP\PBPMPLAB.BAT" -p18F4550 -ampasmwin -k# "button.bas"
Executing: "C:\PBP\PBPW.EXE" -p18F4550 -ampasmwin -k# "button.bas"
Error[105] C:\PBP\18F4550.INC 19 : Cannot open file (Include File "P18F4550.INC" not found)
Error[113] C:\PBP\18F4550.INC 20 : Symbol not previously defined (_CONFIG1L)
Error[126] C:\PBP\18F4550.INC 20 : Argument out of range (not a valid config register address)
Error[113] C:\PBP\18F4550.INC 21 : Symbol not previously defined (_CONFIG1H)
Error[126] C:\PBP\18F4550.INC 21 : Argument out of range (not a valid config register address)
Error[113] C:\PBP\18F4550.INC 22 : Symbol not previously defined (_CONFIG2L)
Error[126] C:\PBP\18F4550.INC 22 : Argument out of range (not a valid config register address)
Error[113] C:\PBP\18F4550.INC 23 : Symbol not previously defined (_CONFIG2H)
Error[126] C:\PBP\18F4550.INC 23 : Argument out of range (not a valid config register address)
Error[113] C:\PBP\18F4550.INC 24 : Symbol not previously defined (_CONFIG3H)
Error[126] C:\PBP\18F4550.INC 24 : Argument out of range (not a valid config register address)
Error[113] C:\PBP\18F4550.INC 25 : Symbol not previously defined (_CONFIG4L)
Error[126] C:\PBP\18F4550.INC 25 : Argument out of range (not a valid config register address)
Error[113] C:\PBP\BUTTON.ASM 197 : Symbol not previously defined (PORTB)
Error[113] C:\PBP\BUTTON.ASM 199 : Symbol not previously defined (PORTC)
Error[113] C:\PBP\BUTTON.ASM 201 : Symbol not previously defined (TRISB)
Error[113] C:\PBP\BUTTON.ASM 203 : Symbol not previously defined (TRISC)