What is the safest way to triple boot Macbook Pro? I recently purchased a MBP 13.3 i5 system, and I'm keen on making it triple boot (Lion, Win7, Ubuntu 11.04). What is the safest way to do this ? I found quite a few websites online, but I'm not sure of whether they are entirely accurate/updated for Lion etc. 

I would really appreciate it if someone could post a link that has worked for Lion/Win7/Ubuntu 11.04.

Also, would this action invalidate the warranty of the MBP ?
Lifehacker's guide to triple booting has worked well for me in the past. You will also definitely need refit. I've seen varying reports of how well refit works on Lion - it seems to be that if you don't have FileVault enabled, you should be fine. Obviously make sure to back everything up before starting - any sort of partitioning/boot loader editing/etc is always slightly risky.

The basic steps are: 


Install refit
Partition all the necessary partitions (OS X, Windows, Linux). Be careful at this step, it can be very difficult to resize partitions that aren't HFS+. You'll need three additional partitions: Windows, Linux, and Linux swap. 
Install Windows, then install uBuntu. 


(Lastly, this does not invalidate the MBP's warrantee.)