IIRC, I believe the VX Owner's Manual talks about the Max Speed in 4WL and I think it's around 60 MPH max (I'll have to verify that fact with the actual O.M.).

My method of driving in the snow is to cautiously drive with prudence in normal 4WH (TOD) and feathering the gas pedal at all times. If the scenario gets very dangerous or becomes very hilly with steep accents and decents, then I pull over/stop and engage 4WL and continue on at <40 MPH (in 4WL) and then later re-engage 4WH (TOD) when the road becomes sane once again and levels out flat.

My very best advice is to have a set of Snowflake/Mountain rated tires on your VX. Since you're VX is 2000 model, I assume you're running 18" rims. Here are probably the two best 18" A/T tires for the VX and are Snowflake/Mountain rated:

A. PRO-COMP - All Terrain in 285/60R18 (31.3" O.D./43 lbs)

B. General - Grabber AT2 in P275/65R18 (32" O.D./44 lbs)