I was asked to pull some data off of a hard drive for a friend. The disk is 3-4 years old so she has no idea what is on it, just pull anything off I can. I don't know if there are any viruses on it so I would like to mount it as read only so I can check it out first. Are there any good solutions for making sure when I mount this thing nothing can come over virus wise?
No need to mount as read only, just completely disable AutoPlay in control panel before you connect the drive.
Once the drive is connected use your AV to scan the entire drive before you start opening files and folders.
Uncheck "Use Autoplay for all media and devices", then hit "Save" button at the bottom.
You shouldn't need to worry about a virus that popping onto your computer from the removable media solely by mounting it unless there is something in the autorun config file. Any antivirus would detect this considering that the drive is 4 years old (along with any other virus). Install a free antivirus program, copy the files, uninstall the antivirus (if you want), done.