Tom's Hardware: "Dubbed Windows Advanced Rasterization Platform or WARP, the new graphics layer for Windows 7 will utilize the system CPU as the graphics engine to assist old graphics cards, and take over completely in some cases. Microsoft indicates that WARP will be fully dependent on how powerful the CPU is in a system, but will require one that supports at least SSE2 extensions.
According to Microsoft, even the lowest-end discrete graphics solutions these days are typically 4 to 5X faster than a CPU-only WARP system. Although the performance differences between CPU-only WARP and discrete GPU accelerated graphics is large, WARP offers several advantages: users will still be able to run their 3D applications fully-accelerated when a video card driver is corrupted, missing, or improperly installed/configured. Systems built to take advantage of WARP from a hardware standpoint will be able to display graphics even when the video card is missing-or toasted. So if you've nuked your graphics card from a bad BIOS flash, fear not on a WARP-capable system. At least you will be able to boot back up until the video card is replaced."