This is the compatibility list from the tomtom website:
NAVIGATOR 5 - Software & Maps of Western Europe - Compatibility
With Maps of Western Europe TomTom can now take you to your destination in 18 countries! Navigate to any address within a country using detailed regional maps, or use the larger maps to navigate across borders to any town or major road with the European major road network.
AcerN30 , N35 , N50 DellAxim X3 , Axim X30 , Axim X3i , Axim X5 , Axim X50 , Axim X50I , Axim X50V Fujitsu SiemensPocket LOOX 610 , Pocket LOOX 720 HPHW6510 , HW6515 , iPAQ H1940 , iPAQ H2210 , iPAQ H2215 , iPAQ H3870 , iPAQ H3970 , iPAQ H4150 , iPAQ H4350 , iPAQ H5450 , iPAQ H5455 , iPAQ H5550 , iPAQ H5555 , iPAQ H6340 , IPAQ HX2110 , IPAQ HX2410 , IPAQ HX2750 , iPAQ HX4700 , iPAQ RX3715 , iPAQ RZ1710 ImateJAM , PDA2K MitacMio 168 O2XDA , XDA II , XDA IIi , XDA IIS OrangeSPV C500 , SPV M1000 , SPV M2000 PalmLifeDrive , One Treo 650 , Tungsten C , Tungsten E2 , Tungsten T3 , Tungsten T5 , Zire72 Qtek2020 , 9090 , S100 SonyClie TH55 , Clie TJ35 T-MobileMDA Compact , MDA II , MDA III ToshibaE-400 VodafoneVPA Compact , VPA III
As you can see, the Zire 31 is not on the list. This does not mean that it definitely will not work (other models have been known to work). What it does mean is that if you purchase it, get it to work and then have a problem with it, Tomtom will not provide any support.
The best bet is to find someone that has tried it before (i'm afraid that I do not know anybody that has) or purchase a tomtom package.
Tom Tom 500 & Palm Zire 31 
Linear Mode
