When I should consider using it?
What is needed to start building applications for it?
I have downloaded an evaluation copy of Windows CE 5 from Microsoft website, how this may help me?
WINCE is normally used for developing the os for devices like mobiles,pocket computers,hand held devices,pmp's,pda's etc etc..
you need to download .NET Framework 1.1, MS visual studio.NET 2003
thats it do start up.Now go ahead.
can get the guidence from platform builder documentations in microsoft website.(windows embedded section)