TwHelper only works in DOS I'm afraid. It was my favorite helper back in the day too.
Today, most players use Swath
http://swath.net/ You can try it for 30 days free before you decide to buy it.
A lot of players also use TWX Proxy - this is not a telnet client you will need Swath, Zoc or putty to run TWX. TWX is a collection of helper type scripts, most of which are available in Swath, but TWX is popular with players who like to write their own custom scripts to play the game with.
You'll find these and so much more at
www.navhaz.com Be certain to look for the returning players tutorial there too.
http://www.navhaz.com/dny_tw_tutorial.txt