What were the infections? on both pieces of equipment. What did you use to clean the PC and how long age was this?
You should also disable the Autorun feature on the USB stick.
Down load Microsoft Tweak UI
to disable Autorun on a specific drive.
After installation, launch Tweak UI, double-click on My Computer in the tree menu on the left, then click on AutoPlay > Drives. This will allow you to change the system settings for AutoPlay/autorun.
Uncheck the drives you want to disable AutoPlay on and click on Apply.
Next, click on the Types in the left tree. This allows you to control whether Autoplay is enabled for CD and DVD drives and removable drives. You may need to restart Tweak UI if it closes after step 2.
Uncheck the box to disable Autoplay for a particular type of drive.
See Totally disable Autorun
for instructions with screenshots.
NOTE: When Autorun is disabled, double-clicking a drive which has autorun.inf in its root directory may still activate Autorun so be careful.