Hands down - HP. My last 4 have been HP and I'll never purchase another. I did give my son a Toshiba, that's proved reliable.
I've bought my last oem desktop. It's some much cheaper just to build your own nowadays. I'm putting together a medium level gaming unit what retail, oem, would cost 2 to 3k for around $400 to $500. A good upgradable motherboard (mobo) and chip (Phenom IIx2) will cost about $200, add an extra $100 if you go with an X4. A higher end mobo with high end video output built in will cost an extra $50 if you want to build a multimedia unit saving you from having to add a high end video card. If you want to go Intel as opposed to AMD it will cost a little more, the i5 and i7 chips are not cheap. There are tutorials all over the internet on how to, that's were I learned some of what I know. Taking apart my old ones was my primary learning experience.