The mirror is about 75cm wide and 50cm high. Can it be hung on a plasterboard wall? What type of screws or nails do I need?
Yup, just like the answer before mine say's you need the proper wall-anchors for it and you will all set.
There are some large mirror that can stand on their own. For a plasterwall, you need something real strong and you need something to be at the bottom of the mirror, supporting it.
Just find the stud behind the wall and center the mirror on the stud. This should solve most of your problem esp. if your mirror is oval or circular. If the mirror is square or rectangulare then one of the above methods will be necessary.
I got mine at the local Wal-Mart store so they are available other places than through the TV and internet adds now.
Weigh the mirror. Yup, I said weigh it. Go to a Mom & Pop hardware store, NOT HOME DEPOT OR LOWES, and ask a clerk what to use. You will just need the proper wall anchors. They will know which to advise you on.