I too have a Dell XPS M1330 which I really enjoy and use extensively - seems since 3 win updates ago, win now shuts down the Nvidia (NV) GeForce 8400M GS - told me there was an incompatibility with a 3D service - not sure what that's about - but - it now will not boot. I had a message my battery was very low (this I knew) and the bios needed at least a 15% charge to allow the NV card to re-engage. Staples Tech declared it dead, my Dell contract expired,
I wrestle with fixing this vs giving up. I did get it a brand new Dell battery- and I got it to boot up (so much for tech suppot).
Its iffy getting it to boot up - I'm on it now, but who knows if it hibernates or I finish for the evening.
by iffy to boot up do you mean that it doesnt always turn on? or do you mean it doesnt always get into windows? if it always powers on thats a good sign...that means its just windows issues...if this is the case you could try removing the old drivers and installing the newest ones...please be a little more specific with your issue