My Dell M4600 running 64-bit Windows 7 can read SDHC cards just fine using the built-in O2Micro card reader. But at present it cannot read SDXC cards. :-(
I realize the original post is 5 years old and was about Windows 8, but you never know what may help someone else. The drivers I found on the Dell site for this device were generally the same for Win7 and Win8.
I haven't figured out how to tell exactly which OZ600xxx model I have, nor am I 1000% certain exactly which driver update to install should I want to try that (Dell has at least two of them that are said to be compatible with the M4600, and I got my laptop from a refurbisher so I don't have a service tag and can't do a scan to get the exact drivers). But I currently have the following drivers showing in Device Manager:
Storage Controller drivers
- O2Micro Integrated MMC/SD Controller version 2.2.1.7060, dated 3/22/2011
- O2Micro Integrated MS/MSPRO/xD Controller version 2.2.1.7011, dated 1/3/2011
and when I insert an SD card, Disk Drive controller driver
- O2Micro SD SCSI Disk Device version 6.1.7600.16385, dated 7/13/2009.
The driver versions currently showing on the Dell site include
- O2 Micro OZ600xxx Memory Card Reader Driver Version 3.0.7.23, A01
released 29 May 2013
last updated 30 Dec 2015
- O2 Micro OZ600xxx memory card reader Driver Version 3.0.7.47, A05
released 26 Mar 2014
last updated 26 Mar 2014
The latter is the one that is mentioned if you look for drivers for the M4600. It also has a later version number, though an earlier last-updated date. The other one turns up in a google search, and is on the Dell site, but I'm guessing it is probably orphaned.
Both include downloads for both a Windows Update package and a self-extracting zip file. I think they are just alternate distribution formats.
EDITED TO ADD: FWIW, I just tried updating my driver, and it doesn't seem to have helped. And now I have an icon in my system tray, saying that "Device driver software was not successfully installed."
AND, FINAL UPDATE: MY SDXC card from Walmart must have been defective (or a fake). I got a new 64-bit card, SDXC, with exFAT file system as they all do by default, and it works fine in both my phone and my laptop. Furthermore, the card's packaging mentioned that Windows 7 and up includes exFAT support, so I didn't actually need to get a new card reader to support it. I think Vista SP1 also supported it, and XP needed a Windows KB update for it.