Go to the drive page of the device and download the appropriate driver (ie. 32bit/64bit), ususally go for the latest and largest driver.http://support.ricoh.com/bb/html/dr_ut_e/re/model/mpc15/mpc15en.htm#Microsoft
you can run the exe and it will install the driver and other utilities/applications for the printer
if you specifically want the INF then :
download and install WINRAR from download.com
then right click on the driver "exe" and choose "Extrat Files"
choose the right location and folder where you can find the extracted files easily
Extracted folder has the INF files you need, browse the path of the folder while installing the printer