Yes you can do this. You just need to make sure the PC has all the required ports for printers, cash drawers etc
There is also no guarantee that there wont be problems due to some future incompatibility with a software upgrade.
One of the reasons why the terminals from all POS suppliers are so expensive is because they are tested and guaranteed to work with the software.
You will also find that the terminals from POS suppliers tend to be older technology which has been tried and tested and usually more robust(rather than streamlined and pretty). Specifically touchscreens which need to stand up to constant use all day long.
A standard consumer touchscreen may not stand up to being used all day long, day after day, year after year.
Before committing to doing a DIY version calculate the cost the worst case life of some of your DIY components(primarily touchscreen in my opinion).
If you buy a consumer touchscreen with a 12 month warranty, expect that it wont last much longer than 12 months in the worst case.
Specialist in creating custom applications for the Micros POS range: 3700, 9700, Simphony FE, Simphony. SIM Scripts, Data Exports, Simphony extension applications, API Creation and integration. If you need anything please contact me via my website