OpenDNS - Parental Controls
The free option could give possibly slightly faster internet access, but you might as well use free google dns servers - 8.8.8.8 and 8.8.4.4
The benefit of OpenDNS really lies with their subscriptions which could help you browse internet more safely.
In general there is only one (mostly) safe way to secure potentially compromised computer - Full wipe. If windows compromised - running A/V checkers is already too late.
Really nasty stuff could even modify PC permanently and even full wipe won't help
One option before full wipe is to do scan with Kaspersky Rescue Disk -
https://support.kaspersky.com/4162 - download the ISO and burn it to cd. Boot the PC from the disk and update the database and run full scan. It will take a while, but it's worth the wait.
I highly recommend to get a Google Chromebook and hard limit your online banking/trading only to this device.
Chromebooks: Overview