Disappointed to hear that Lenovo's service is that bad.
My current desktop is an IBM ThinkCentre -- built by Lenovo, but branded and sold by IBM. That was back in 2003. I did a major overhaul in 2007 -- replaced the hard drive, optical drives, installed more USBs, etc. So far, I'm very satisfied.
Now that it's 10 years old (or, will be in a couple of months) it has started acting flukey. I'm building my replacement ... but I'm definitely not setting any speed records! I'll let you know my progress in a few weeks!