I think there's a rootkit on my win7 PC

download Malwarebytes Anti-Rootkit from here

• Unzip the contents to a folder in a convenient location.
• Open the folder where the contents were unzipped and run mbar.exe
• Follow the instructions in the wizard to update and allow the program to scan your computer for threats.
• Click on the Cleanup button to remove any threats and reboot if prompted to do so.
• Wait while the system shuts down and the cleanup process is performed.
• Perform another scan with Malwarebytes Anti-Rootkit to verify that no threats remain. If they do, then click Cleanup once more and repeat the process.
• When done, please post the two logs produced they will be in the MBAR folder... mbar-log.txt and system-log.txt

Any of these are good Best Free Rootkit Scanner and Remover

and you might like to try this as it runs from boot
Download Kaspersky Rescue Disk 10 < takes a while but will avoid using the OS and runs from power up.

julianbury,

Please use the following diagnostic tool. It has a powerful detection mechanism, and may help us get to the root of your issues:

Please use the Farbar Recovery Scan Tool.
Download: Farbar Recovery Scan Tool Download
Select the version that applies to your system.
Save it to your Desktop.
Double-click the downloaded file to run it.

When the tool opens click Yes to the disclaimer.
At the program's console, press the Scan button.

When done, the tool produces a log, FRST.txt, in the same directory from which the tool is run (Desktop).
Please provide the FRST.txt in your reply.

The first time the tool is run, it also makes another log: Addition.txt
Also post the Addition.txt in your reply.

Julian have you run any of those rootkit scans or that Kaspersky one I linked yet?

FYI. Malwarebytes v2 includes their rootkit scan.