The Texas Instruments PCIxx21/x515 driver is the driver for the PCIxx21/x515 memory card reader. It doesn't occupy much space on your hard drive and I don't suggest you to remove it. But if you want to remove it you can use Add or Remove Programs feature:
If you use Windows XP or bellow you can go to Start > Control Panel > Add or Remove Programs. In the Currently installed programs box, click on the program and then click Remove.
If you have Windows Vista or above you need to go to Start > Control Panel > Programs > Programs and Features. Select the DivX application and on Uninstall.
After that, try running AdwCleaner to make sure that there are no leftover rogue registry keys or toolbars in your system.