So, I have this problem that always that I try to use my PC as a guitar effects modeler, a virtual synth, etc. I always get delay from what I play and what I hear (like 0,2s or so). The DAW I'm using is reaper. I don't think the computer's hardware is causing it either, as its processor is an Intel Core i7. Ideas or clues why is this happening? Are there any settings I need to change?
First of all, make sure you've installed all the drivers that are needed and/or update them.
I used to have the same problem with my Focusrite Scarlett 2i2, even after I had all the drivers needed installed. The problem was that I was trying to listen to the outcome through the monitors of my PC, which were not connected to the audio interface (focusrite). To solve this, I usually connect my headphones straight to the interface. The best solution would be to get good monitors and connect them to the interface, but this requires some money, in order to be some decent ones.
Latency is not about the power of your computer. It's about the soundcard, its drivers and their settings.
If you have only onboard audio, try installing the free driver ASIO4ALL. But the real answer is an additional audio interface (sometimes generically referred to as a 'soundcard' even when it's an external USB device) with a dedicated ASIO driver. This will enable sub-10ms latency.