That's not a recognized Compaq model number, so look on the sticker under the laptop for the actual model number and search for drivers
for Windows 7 on the Compaq Support Downloads webpage for that model. You'll want the card reader drivers. If not trace the actual hardware using Hardware Identification.
Is this Windows 7 preinstalled at factory or an OS installed by the previous owner? Does it have a COA sticker proving it's genuine Windows on the bottom of laptop, with a Product Key in case you need to reinstall it? If not once you get the drivers installed I'd save a Windows 7 backup image to use in place of reinstall. Backup Complete Computer - Create an Image Backup