I am sure you dont mean drain the system - you mean bleed the air out? - If you know how to refil the system then you probably wouldn't have asked this question (stupid me)
To Refill - look for a filling loop on the pipework somewhere under the boiler (not sure if this is built in on a micron) should be a braided metal flexi pipe with a valve at either end.
Turn the valve to let in water while keeping an eye on the pressure gague on the boiler - making sure that you dont let it go over 1.5. shut off valve when 1.5 - then bleed air from radiators. - repeat until all rads are done then make sure gague is between 1 and 1.5 fill as needed, rads should get hot.
If you are really stuck with this or have no idea of what i just wrote - then reply to this with an email address and i can put some diagrams in that.
OR depending where you are in the country and how big the property is - a nice plumber should do this for about £35.
Stewiesnake, November 2008
