Sometimes it happens! You buy something at your local department store, the clerk forgets to remove the magnetic tag from your purchase and the store beeper never went off! If you don't have time to run all the way back to the store to have it removed, you'll have to do it yourself, And though it may seem impossible, it can be done.
Find a very strong magnet, similar to one in your computer's hard drive. You need a magnet stronger than the one inside the security tag. Find an old hard drive at a computer repair store or a thrift store that sells old computers for really cheap.
Place the magnet on top of the security tag. You will feel the force of the two magnets pull together. Twist the hard drive magnet to loosen the magnet that is inside the security tag.
Lift the hard drive magnet off the item that the security magnet is stuck on. The top of the security magnet should lift with the hard drive magnet. There should be a pin that is now stuck in your item. Pull it out and you are security-magnetic-tag-free.
Security tags should only be removed if the item was legally purchased and the tag was accidentally left on the item.