Ok, Mass Storage Controller on the W4605 is referring to the SD slot like I posted above. It is a Texas Instruments PCIxx21 Integrated FlashMedia Controller. It's driver can be found on Emachines.com, go to support, select Notebook, select W-series, select model W4620 (yes, I know this is not the W4605 model we're in discussion with here). Under the W4620 drivers, you will find everything you need for the W4605. The Mass Storage Controller driver you are looking for is called Media Card Reader driver on the Emachines driver page.
I updated the driver from the Device Manager and told it to look in the folder where this driver was. Windows picked it right up. I tested and it works fine. Also, the wireless drivers for the W4605 is on this page too. It looks to me like all of the hardware between the W4605 and the W4620 is the same, except for maybe faster processor and more memory.
Hope this helps.