Right, here is what to do: The answer according to X:

1. Take your girlfriend horseriding to show her how much you love her. While you are there, steal some horse tranquilisers.
2. Find a company that does house-letting. Say that you are looking for somewhere with a basement. Make an appointment to view and say that your wife/girlfriend will attend.
3. Say that you are really busy to one of the girls at work and you can't go to look at a new property you are visiting. Ask if she will go and have a look from a woman's point of view.
4. Rent the property and do all the paperwork through a yahoo account. Hack into HR records and do it in someone else's name and use the details of someone who recently left the company.
5. Kidnap and abduct the girl from the office, using the tranquilisers you earlier got from the horse riding.
6. Keep her chained up in the basement of the new house, doing whatever you like. until a) you get bored or b) she dies
7. Eventually, make a small brick sitting area/workbench in the basement. Bundle her body into this, securely wrapped in plastic with some caustic lime drizzled over her.
8. Firmly brick her into the structure and tidy everything up carefully.
9. Off-hire the house, using the same details.
10. Continue with life happily with your girlfriend until you run into some other evil slapper who needs punishing.