I've found the following links useful so would like to share them with you. If you have any recommendations for other software please drop me an email.
A fully functioning FREE virus protection program with regular updates
Click here to download - if this link does not work let me know, go to Grisoft yourself and find the free version. Carefull, there is a version you have to pay for.
CCleaner is a freeware system optimization and privacy tool. It removes unused files from your system - allowing Windows to run faster and freeing up valuable hard disk space. It also cleans traces of your online activities such as your Internet history. But the best part is that it's fast (normally taking less than a second to run) and contains NO Spyware or Adware! :)
More than just a thumbnail viewer, can't recommend this software enough. Perfect to organise, edit and print your digital photo collection. Very fast and easy to use interface plus IT'S FREE