A B737-400 FO SUFFERED A COURSE DEV WHEN ATTEMPTING A HAND FLOWN ILS INTO KTS; AK. FLT RECEIVED AN ENHANCED GPWS SIGNAL.

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I ROUTINELY FLY INST APCHS IN THE WX USING RAW DATA AND FLT DIRECTOR OFF SO AS NOT TO LOSE MY INST FLYING SKILLS. THIS NIGHT; FOR THE FIRST TIME EVER; I INADVERTENTLY SET MY EHSI MODE SELECTOR TO 'EXP NAV' INSTEAD OF 'EXP VOR/ILS.' THIS MODE DISPLAYS LATERAL AND VERT NAV GUIDANCE ORIENTED TO AIRPLANE TRACK WITH THE FMC AS THE NAV SOURCE INSTEAD OF THE LOC AND GS. THERE WERE SEVERAL CLUES I DID NOT PICK UP ON DURING THE APCH. 1) BECAUSE OF STRONG HEADWINDS ON THE PROC TURN OUTBOUND; I DELAYED THE INBOUND TURN TO KEEP FROM OVERSHOOTING THE LOC. I HAVE DONE THIS NUMEROUS TIMES ON THIS APCH WITH STRONGER WINDS; AND WAS SURPRISED I OVERSHOT THIS TIME. I REINTERCEPTED WHAT I THOUGHT WAS THE LOC. 2) I PROGRAMMED A VNAV PATH TO THE RWY ON THE CDU WHICH GAVE ME A GS ON MY EHSI WHICH IS WHAT I NORMALLY SEE IN 'EXP VOR/ILS' MODE. HAD I NOT DONE THIS; I WOULD NOT HAVE HAD THE EHSI GLIDE PATH. 3) THE CAPT SELECTED EGPWS AND I HAD WX RADAR. MY EHSI SHOWED NUMEROUS WX RETURNS WHICH ALONG WITH THE YOKE; BLOCKED MY VIEW OF THE MISSING LOC FREQ THAT SHOULD HAVE BEEN IN THE BOTTOM R CORNER OF THE EHSI. 4) I DID NOT NOTICE THAT 'TRK' WAS DISPLAYED AT THE TOP OF EHSI INSTEAD OF 'HEADING' (BIG CLUE). 5) THE CDI WAS TOO STABLE FOR A LOC SIGNAL. I THOUGHT I WAS FLYING A GOOD APCH. APPROX 2000 FT MSL; SEVERAL THINGS HAPPENED AT ONCE. WE BROKE OUT AND THE CAPT SAID THE RWY LIGHTS WERE SLIGHTLY TO THE L AND THE EGPWS TRIGGERED 'CAUTION TERRAIN.' WE BOTH CHKED OUR NAV SETUP AND I ASKED FOR WIPERS BECAUSE MY FORWARD VISIBILITY WAS LIMITED DUE TO RAIN. I STARTED TO CORRECT BACK TO CTRLINE AS A 2ND AND 3RD 'CAUTION TERRAIN' SOUNDED. AT THE FIRST 'CAUTION TERRAIN;' THE CAPT SAW YELLOW TERRAIN TO THE R OF OUR COURSE. OUR EGPWS GIVES US THIS 'SOFT ALERT' APPROX 60 SECONDS IN ADVANCE OF TERRAIN AND IS REPEATED AFTER 7 SECONDS; IF STILL IN THE CAUTION ENVELOPE. DURING A TERRAIN CAUTION ALERT; AREAS WHERE TERRAIN VIOLATES THE TERRAIN CAUTION ENVELOPE ALONG THE ACFT TRACK AND WITHIN +/-90 DEGS OF ACFT TRACK ARE PAINTED IN YELLOW. AFTER CORRECTING TO COURSE; IT WAS AN UNEVENTFUL LNDG. I SHOULD HAVE DOUBLE CHKED MY NAV SETUP EARLIER AND PURSUED THE NUMEROUS CLUES SOONER. THE CAPT WAS BACKING ME UP MAINLY WITH THE HUD AFTER RECENTLY BEING CHKED OUT ON THE SYS. IN THE FUTURE; I WILL HEED WARNING SIGNS EARLIER AND DOUBLE CHK EVERYTHING; AND MAKE SURE THE CAPT IS BACKING ME UP USING MORE THAN 1 SYS. I AM VERY GLAD WE HAVE THE EGPWS WHICH PROVIDES MORE ADVANCE NOTICE THAN THE OLD SYS.