When you rolled back the appropriate Intel driver, setting it to the default windows driver, you mentioned that you noticed better performance in terms of speed. Now here's the catch; almost all the popular operating systems including Microsoft's come bundled with numerous set of device drivers for well known chipset manufacturers including Intel. I am assuming that it could be the case that the driver that you installed from the CD was not the right one and when you rolled it back to Microsoft's, the driver it installed was in accordance to the chipset and upon speed test you experienced slightly better performance, but since I do not like making assumptions; here's some information I'd like you to write back so that we can get to the right solution.