What quekky recommended (Autocad 2006 and 3ds Max) are some of the top of the line programs for doing all 3 Dimensional object designing including interior designing and architecture.
But if I read your message correctly...you are getting a new home in a week's time and you just want to dabble in designing how your new home will look with the right colour, furnitures, wall and room fixture..etc All to help you to visualise how your new home/rooms will look. If that is your only aim, I have to tell you ..programs like what was recommended cost a few thousand dollars ( you can buy a few Nikon D50s for what you pay for those software original) PLUS the most crucial reason you should not even be considering any software to run on your PC or Mac is because...almost all this kind of programs have a very steep learnign curve. By the time you learn to use them competently to design your home..you have already moved in and stayed in it for a few months if not longer.
Take my advice...it is alot easier to do it with paper and pencil and lots of colour markers and visiting and/or buying interior design books. I do something do retail store design, exhibtion booth..etc in my work and even I seldom would use just a computer to do it, I will mix it up with free hand drawing especially when I am playing with fabrics, texture surfaces..etc Som eof this stuff are too troublesome to digitize, render..etc especially if you have a short turn around time to do it and still have time for production to take place. trust me, if you are not PC savvy, have problem with colour coordinating, drawing objects, understanding 3D environment, learning some programming codes...etc. Those software are really very tedious to learn quickly. You can get cheaper software but being cheaper, there will be limitation too and still a need to learn how to use the software. Drawing a basic room is easy but you need to learn to create all the other more complicated objects and placing them in a 3D environment with the right colours, textures, tone, lighting..etc.
Advertising and the way some people would say how easy this program or that design program is soooo easy to use...that is just crappy marketing talk. The more often they say it is easy..it usually is not.