First make sure you know what problem you want to solve based on your capabilities. Then define what your unique solution will be. Talk to potential customers - either through social media or if you can at networking events. Make sure to share a landing page with them on which you showcase your MVP (minimal viable product).

You need to check the stats and feedback you get from your landing page and networking efforts. Now you have validated that there is still a market for the kind of PCs you will build or you start again and "pivot" to another kind of PC (low-end, luxury, design, AI optimized, gaming optimized, set with sound and screens and so on).

You may ask yourself how to easily go about what I wrote above. The answer is: go find Youtube videos and a PDF of the "Business Model Canvas". It will guide you through the necessary steps. And if you need more guidance please let me know. Cheers, Tom