Gigabyte Z68XP-UD3-iSSD Motherboard: 20GB SSD On-Board

You should read the article and even some of the comments before posting.
Smart Response Technology

The on-board SSD is not used as an OS partition.

Most of the posts complaining that 20gb onboard ssd isnt enough are by people who clearly do not understand the SRT. All it does is copy the most frequently used files to the 20gb drive. The first few tims you use it you won't notice much of a speed difference - write time for the first episode is actually slower because it copies it to both your hard drive and the SSD

OVER TIME you will notice a tremendous speed gain. Onboard SSD are most certainly not meant to store all of windows and your most commonly used games/apps. The onboard SSD is DEDICATED to retaining fast access to frequently used routines. You could use it like a conventional hard drive, but you would be foolish to do so.

This makes a lot of sense if you think about it. Transferring data thru cables takes time - the longer the cable, the more time required. (All other variables being equal.) That's why processor cache is so important, L2 cache, L3 cache, consider the onboard SSD as if it were a L4cache.

Only use this mobo with onboard SSD with SRT enabled. THEN go buy a 240Gb SATA iii drive, install windows on it, and see how fast your system goes. (use the shortest cable that will work in your system too!)