Just wanted to know how much wattage I need when I go shopping for one of those power inverters? I have an IBM Thinkpad R51.

We take the laptop everywhere to watch dvds on trips. My converter is 160 watt with 360 watt max. It was about $40.

Cool, I was considering getting the 200 watt one so I guess I'm safe. Thanks!

Why not merely buy a 12 vt power supply made for your computer, I run my laptop for GPS, watching DVD and listen to CD all the time.

The car adapter for an IBM laptop would be at least twice the price of a power inverter. Plus the power inverter can power other 12V devices we may need.

I have run power inverters for about 8 years for all sort of things, you will find some issues ( they have to be unpluged to turn car on and off)
And they normally make noise at least after a point. Also some will have power increase and decease as the alternator causing some power flux.

I won't try to get into the sine wave difference in the inverters to true 120 vt power but often this difference is hard on computer equipment.

Yes they are often more expensive, but also you may want to check walmart for some that fit various models, I have seen some with prices coming down