LOS ANGELES – With the launch of its Surface tablet computer, Microsoft is becoming a genuine "frenemy" – part friend, part enemy – to its longtime manufacturing partners.

Since its founding 37 years ago, the Redmond, Wash., company has had a mutual understanding with makers of computer hardware: Microsoft creates software. Companies such as Dell, HP, Acer and Lenovo pay Microsoft a licensing fee to place the Windows operating system on the desktop PCs, notebooks and other gadgets they market to consumers.

Now, Microsoft is complicating the cozy relationship by making and marketing its own tablet computer. The company announced Tuesday that the Surface will start at $499 when it goes on sale Oct. 26. The new tablet is set to invigorate an already hotly contested market for touch-screen computers. But for first time, Microsoft will be in head-to-head competition with partners that help generate sales for its $14 billion-a-year Windows software business.