The game I'm thinking of:

Played it on PC in the 90's

It was in space

Loads of trash started flying across the screen. 

You had to shoot the trash and destroy it.

That's all i remember.

Can you guess the game? Any help appreciated!

EDIT: Thanks for the help. The game is called Math Blaster! Here is a video. You had a great childhood if you played this game :) 

http://www.youtube.com/watch?v=7F4_kzb_vzg

anybody know?

Darude-Sands...
Superman 64

nope. it wasn't a sofisticated game. it had 1 screen and you pointed and shot all the rubbish floating through space. Come on surely somebody knows this!

Almost sounds like the early Touhou games on the PC-9801... Except Touhou is in Gensokyo, not in space.

There's hundreds of games where you shoot stuff in space though. Makes it difficult to guess. lol.

Lol sounds like a game I made in school for IT =P

pft Touhou isn't a game.

You're right. It's not a game... It's an ecosystem!

snood?

Sounds kind of like Asteroids?