A PA28 PLT; ADMITTEDLY BARELY IFR CURRENT; FLEW AN ACFT HE WAS NOT FAMILIAR WITH IN IMC IN A90'S AIRSPACE.

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DEPARTED BED IN AN ARROW FOR PRACTICE APCHS AT LWM IN IMC. AFTER LWM ILS RWY 5; I PLANNED TO HOLD AS PUBLISHED AT THE LWM VOR. HOWEVER; UPON SWITCHING MY VOR #1 TO LWM (112.5); I OBTAINED A NONSENSICAL OBS INDICATION. I DOUBLECHKED THAT THE STATION WAS TUNED AND IDENTED CORRECTLY. I INFORMED ATC THAT I WAS HAVING TROUBLE WITH THE VOR; AND REQUESTED VECTORS WHILE I DIAGNOSED THE PROB. MY VOR #2 AND MY VFR LORAN WERE GIVING SENSIBLE AND MUTUALLY CONSISTENT READINGS. AFTER A FEW MINS; I REALIZED THAT MY VOR #1 WAS IN RNAV MODE RATHER THAN VOR MODE; AND WAS INDICATING THE RADIAL TO A DISTANT WAYPOINT INSTEAD OF THE VOR ITSELF. I SWITCHED TO THE CORRECT MODE AND THE REMAINDER OF THE FLT WAS UNEVENTFUL. THE CONFUSION AROSE; IN PART; BECAUSE IT HAD BEEN SEVERAL MONTHS SINCE I'D FLOWN THE ARROW (EXCEPT FOR SOME VFR FLTS WITHOUT USING THE VORS). ALSO; I HAVE ALMOST NEVER USED THE RNAV EXCEPT IN VOR MODE. I HAD JUST THE BARE MINIMUM OFFICIALLY REQUIRED IFR CURRENCY (VIA AN AST 300 FTD); THOUGH I'D BEEN MAINTAINING PROFICIENCY; UNOFFICIALLY; VIA A PC SIMULATOR; WHICH I FIND VERY EFFECTIVE FOR KEEPING UP MY PROC SKILLS. BUT THE PC PRACTICE DID NOT INCLUDE USE OF AN RNAV. ALTHOUGH I INITIALLY HAD ENOUGH SITUATIONAL AWARENESS TO BE CONFIDENT THAT THE VOR INDICATIONS WERE WRONG; I FOUND THAT MY ORIENTATION QUICKLY DEGRADED AS I TRIED TO MAKE SENSE OF THE ANOMALOUS VOR INFO. THE RESULTING CONFUSION; COMBINED WITH THE BASIC DEMANDS OF SOLO FLT IN CLOUDS WITH NO AUTOPLT; MADE IT TAKE MINS INSTEAD OF SECONDS TO REALIZE WHAT THE PROB WAS. FORTUNATELY; THE NAV DISORIENTATION OCCURRED OVER FLAT TERRAIN AND UNDER RADAR CONTACT; SO THE EXPERIENCE WAS FAIRLY BENIGN AND EDUCATIONAL. (I WOULD NOT HAVE ATTEMPTED SOLO IMC FLT UNDER MORE CHALLENGING CIRCUMSTANCES WITHOUT MORE RECENT EXPERIENCE WITH THE ACTUAL ACFT'S AVIONICS.) ATC WAS VERY HELPFUL.