Hello apico. Yes I did this a while back. My laptop crashed twice in just over 100 gigs. The second time I was sitting in with a function band at a wedding and it was during an exposed piano bit in the first dance. Went back to hardware for live after that.
If it's an electro gig - people dancing at a club or experimental stuff - you can get away with a crash or two if you're not on your own. Get a beat going on something (or a digital soundscape) - even a track on an mp3 player - and reboot.
For exposed gigs where you are playing a definite part - and the band is relying on hearing certain riffs and chords - you need to think about how serious a crash is and decide if it's worth it.
I used an Acer laptop with 2 GIG RAM, Intel Dual Core 1.66GHz and ran off the internal drive.
I ran Native Instruments Kore software hosting a few VSTs, some of their soundpacks and the Kore library. It was as fairly stable. I used the Kore 1 hardware controller (which had audio outs).
This is an area I've looked into a lot - and I'm going back to a partial VST live rig towards the end of this year.
Give us a few more details about
(1) what you want to run
(2) the live situation you'll be using it in
That's a long reply - my short one if money weren't an issue - get two Muse Receptors an run them both with an A/B switch in case one locks or goes down.
You can run the Receptors without a screen - one of the niggles of taking a laptop on stage - punters will want to know what it's for and how much of the show is karaoke.
BTW - I couln't justify the price of a couple of Receptors. I'm looking at a rack mount PC - maybe from Inta Audio here in the UK. I still intend to use Kore as a host and my Kore 1 controller for audio and midi ins and outs.
Good luck.