1. Before you go ANYWHERE on the web, update Windows, your antivirus software (note that most new PC's these days come only with a time-limited trial version; you'll eventually need to buy that software or install another one after uninstalling the one that came with the PC) and install a good firewall.
2. New PC's from large vendors come with a lot of preinstalled stuff that you may never use. If that's the case, uninstall those apps.
3. After all this, you'll need a good Registry cleaner to get rid of the trash; fret not, there are a number of good free ones out there.
4. Then, decide on a plan for backing up your data, obtain the necessary software and backup your entire C: drive. This will be your recovery disk, and NOT what the vendor gives you.
For more good advice, see Toni H.'s post in this forum. It's the very first post on the forum home page.
Paul