When I was a kid, maybe 9 or 10 years old I played on my brothers pc. It must've been around the year 2000. I used to play a lot of AgeOfEmpires1 and 2, also TonyHawksProSkater2 and GTA2 and also a game I absolutely loved, but couldn't make any progress in.
I don't recall the name of it and I don't know too much about anymore, I don't even know if it was a full game or just a demo.
Short description of what I remember:
It was very colorful and in 3D, you played a little guy and you started on top of a mountain and you had to slide down that mountain on something, iirc it was a lid of a pan or something like that.
The montain was coverd with snow and ice and at the end of the track you even slid on gras a bit and then eventually landed in a little lake.
Once you climbed out of that lake there was a phone box somewhere, but I don't remeber what that was for, I guess you were able get up the montain to slide again with the help of that phone box(I'm not sure if it was really a phone box

).
But somehow you could get away from that area. The other place where you could go was also very colorful, I remember rainbow colored streams. There also was a little well and you were able to go into that well and dive, but unfortunately you needed a diving bell... I never found a diving bell.
And thats all I remember.
Would be pretty sweet if someone knew what game I'm talking about =)