get your windows updated and patched (the security flaw that conficker attacks was patched back in Oct last year by MS). Also make sure you scan your PCs with anti-malware and anti-virus programs at least once a week. I recommend Avast AntiVirus (free) and Malwarebytes' Anti-Malware (also free), or do an online scan via http://housecall.trendmicro.com/ or at the websites of most of the top antivirus companies.