With the recent ransom ware that has gone wild in the world using a security hole in Windows it is important that your Windows be up to date. Microsoft had previously released a patch for Windows 7 and 10 that blocks the hole the hackers are using for this ransom ware.
If you are using Windows 10 chances are that your machine has all the latest patches as Microsoft has set Windows 10 to update automatically by default. To do a manual update (which you can do and automatic be turned on, besides if it was turned off) type in the search button beside the Start button the word update. A list will appear. Click on check for updates and it will then go check for updates and either install any found automatically or prompt you with questions to install. If asks if you want to install updates answer yes. After the updates run or during them, the system may restart. Once it finishes I suggest restarting the system to make sure all are active.
Even if you know your Windows 10 is doing automatic I suggest above and also to reboot system as some updates only take place at startup or shutdown.
If you are using Windows 7, click on the Start button and then choose Control Panel. Then click System and Security. Under Windows Updates, click Check for Updates. It will then run a check which may take several minutes and then will give you a list of updates, and they should all be chosen by default (if any are not it usually means they need anther update first) and do updates. When it finishes you may need to restart system and then I suggest run it again so if any had depended on previous you just installed, you can get them. Then restart system at end.
Also make sure your antivirus is updated.