Modifying the OS would only cause trouble if you sent the system in to have it repaired without the original OS type installed. If you call in for support and they find out that you have a non-standard OS installed, one of the first things they will do is ask you to reinstall the original OS from your restore disk. They wont even care that you have to hook up an external cd/dvd drive. You would need to do this before sending it in for service related to the hard drive or OS or whatever, as they would attempt to boot it when the tech tries to troubleshoot it. I hate to say it, but you should error on the side of caution if you are not familiar with modifying your computer in any way related to hardware. OEMs are not compassionate when they find out that you have been playing with hardware.