I've just bought Dell mini9 inspiron with builtin simcard reader for mobile broadband
I was wondering, I have a 1gb data bundle pack on my Orange mobile contract... Could I just put this in the laptop and use the 1gb through the laptop instead of my phone itself? Would this work ok and I wouldn't get charged anymore? I tried calling Orange and all they said was this would be "unadvisable"

I would see why you can't use it.

just as long as you don't use it excessively, you should be fine.

Agreed

It is against the T&C of all the mobile operators to use a phone SIM as a Mobile BB connection, but as long as you keep the data use down it should be OK. Part of the problem though, is that desktop browsers use much more data than mobile phone browsers as they have all the graphics and rich content turned on. You may quickly use up more than 500MB (remember this is counted for traffic both upstream and downstream, unlike home BB systems) from which point you may be paying up to £1 per MB of data.

The operators have the technical ability to determine if you are using the SIM in a phone, but many people do this without any intervention.

I personally use a 3 PAYG SIM in my netbook, and buy the £5 per month 1GB mobile internet add-on and it works fine.