I'm thinking of getting an inexpensive inverter for the car, to charge my Lenovo Thinkpad laptop from the 12v source.

After doing a bit of research I found a few posts out there that implied that using an inexpensive inverter with a modified sine wave (as most of them are) might damage a laptop.

But many of the brand names in laptop devices sell these things, and laptops are listed as a device that can be charged.

For example :
Duracell DMPI-175Inverter (prob. a Xantrex)
Xantrex XPower Inverter 175 Plus
Kensington Ultra Portable Power Inverter 150

I can't seem to get the definitive answer on this.
I know a pure sine wave inverter would be the best (and more expensive), but is it ok to use the modified sine wave types?

 

I can't say either way, except that I do it routinely.