You guessed it (probably from the headline): backups. Once again I'm going to lecture you on the computing equivalent of flossing your teeth. Bottom line: Do it now or regret it later.
Actually, I'm not going to lecture you at all, but rather steer you to a PC World feature I wrote last year: How to Prevent a Data Disaster. It has all the information you need about creating a diversified backup plan, which for my money is the only way to ensure total safety.
The one item that needs updating is the now-defunct DocSyncer, which made it possible to sync your local documents with your Google Docs account. Fortunately, a free tool called OffiSync can take its place.
Now go forth and enjoy that new PC! And let me know if you run into any other hassles that need solving.