It's slow hardware, as others have said, but if it suddenly feels a lot slower than it used to, it's probably some software that you installed, most likely some malware or one of those "helpful" utilies that thrashes your hard drive looking for ways to speed up your PC without ever actually making any improvements. Sometimes you can find that you've installed two antivurus tools at once, McAfee and Norton are often installed without people wanting them as part of another installation, because people click next without unticking the box for bundled crapware like that.
1) Go to "programs and features" in the control panel, sort by installed date, and look for anything suspicious installed recently. Remove anything that's a media player, "Adobe Flash", codec pack, toolbar, PC speedup, registry fixer or other utility that you didn't specifically download for yourself. Most of these things are malware or malicious in some way and people rarely install them intentionally.
2) Make sure your Antivirus is up to date and do a full scan. Avast and Panda are two reasonably decent free ones if you don't already have any AV.
3) Download and run Malware Bytes Anti Malware: https://www.malwarebytes.org/mwb-download/
If your PC is clean, free of malware, free of bloated utilities and still running like a dog, then it might be time for a hardware upgrade - one of the easiest things to do that makes a big difference, even on netbooks and nettops like yours is to change the slow hard drive for an SSD. Some retail kits even include cloning software and a cable that makes transferring your Windows installation and programs a breeze.