Martin got a popup that says that Microsoft suspects malicious activity that's causing "system breakage." Leo says it's a scam. A popup doesn't mean he's infected, but if the grammar is bad, then it's likely a scam. Since Martin is using Internet Explorer, Leo advises updating to IE11 and run his updates. Leo also suggests using Google Chrome instead. It's far safer. He'll never see those popups again with Chrome.
If Martin is using Windows 8, then he's got Windows Defender built in. If not, then he should download Microsoft Security Essentials.