In Orbiter, no, as has been said.
In real life, it depends: How much does the planet's orbit have to change before you consider it "moved," how long are you willing to wait, and how much damage are you willing to do to the planet?
1. The average planet-sun distance should change by one diametre of the planet.
2. Let's say...the time it takes to complete one half of it's orbit around the Sun
3. in the case of Earth, the surface should still be habitable for humans after the orbit change.
Now someone get your astrodynamics equations out and calculate the mass/force/size of the rocket needed to do this to Earth.
P.S.:Andy44, so "all" you have to do to move Earth is to put together a giant (which is a giant understatement in itself) ion thruster that reaches outside of the Earth's atmosphere? If I remember correctly, Ion thrusters typically have exhaust velocities in the 10-20 km/s range, which is easily above the Earth's escape velocity. The fuel mass would be negligible compared to a conventional rocket engine, and since it's on Earth, you can always build a few dozens of giant nuclear power-plants around it for power. The thruster would be located on the equator and only fired for a few hours a day when the Earth is positioned properly to give it a prograde boost. In a few months, the delta-V should built up even with a relatively low acceleration - say, on the order of .1 to 1 m/s^2.
Disclaimer: This is a semi-drunk 2am post, please go gentle on any obvious errors. I didn't do any calculations and I acknowledge that this could never work.
P.P.S.:Ok, math time:
If we assume 1 m/s^2 acceleration for 6 hours a day (with thrust vectoring to somewhat compensate for the Earth's rotation or something) for six months, the total deltaV would be 1080 m/s, which is quite a chunk of the Earth's orbital velocity, 29783 m/s.