Wall power outlet question

Hello, I'm new here but this looks like I've found heaven!

Anyways on to the question...
I'm planning a small grow with a 400w HPS light. However, the place I'm going to be doing the grow at is a very old house. So, it only has 2 prong power outlets on the walls, here's a pic of what I'm talking about: http://www.rd.com/images/tfhimport/2003/20030401_Ask_Handy_page003img001_size2.jpg

I have access to some 2 prong to 3 prong converter things as seen here: http://www.shoplet.com/office/limages/EFEL0714.JPG
However, I don't know if it's safe to run my light through one of the power outlets using a 3 prong converter....

Here's what I was planning: To install a 2 to 3 prong converter on the wall outlet, then plugging a power strip into that which would have the light and a few other things plugged into it.
Would this be a safe thing to do??????

My only alternative would be to run an extension cord from the next room which has a 3 prong power outlet installed for the air conditioner.

THANKS IN ADVANCE !!!!!

Well you could do that but get a high voltage and amp adapter as these can melt and catch fire I have melted a few in the years or you could spend 2 bucks and buy a new wall outlet at home depot with the grounded 3 prong setup.It takes about 3 minutes to swap a new one out. Turn the power off to that room at the fuse box.Take the screw out of the cover plate.There will then be 2 screws under that holding the old outlet in place take them out.Tug the outlet out of its box. There will be 2 wire.Probably a white and black or 2 white or 2 black.these are held down by a tightened dow screw on each side of the outlet undo both and take the wires and put them on the new plug just like the old 1 1 wire on each side.Reassemble and your done.Turn power back on and your good to go..

Fletch is right. I would just change the outlet. That would only cost you about 5 bucks vs. buying a high gauge extension cord. Trust me you'll need a high gauge if you using a 400 watt lamp. Unless you want the house to burn down.

OK! Thanks for the fast responses!

I'll probably end up buying a whole new outlet like you both mentioned...

However, I failed to mention in my first post that the 2 to 3 prong converter I have has a little metal tab you must screw into the middle hole on the outlet cover. Here's a pic that shows you almost exactly the one I have: http://www.american-allergy-supply.com/dn3000/61-2720plug.jpg

The one I have says this on the package: "Grounding Adapter" "Converts an outlet for a 2 prong plug to an outlet for a 3 prong grounding plug".

So does this change anything? Or is my best bet to just install a new outlet like you suggested to begin with????

THANKS AGAIN!

I cant' say for sure if that'll work or not because I've never used them. I try to stay away from rigging stuff and just do it the right way.

if you have a power surge your light will not be protected. this goes for your timer being grounded as well. and when you use the powerstrip there might be only one of the six outlets "protected" make sure your light is plugged into that one. i have an older wiring system and if i plug more then my thousie into what outlet it trips the breaker. i have 3 outlets for two lights and 4 fans.