so i bought an old windows XP computer (vista capable) with hopes in using it as a guinea pig, i have always wanted to try upgrading and/or building my own computer but i haven't had the time or the know how to do so, im hoping that this computer can serve as my guinea pig for a bit. i know what i can upgrade but i know nothing about compatibility or anything like that, and i know better than to buy some random pc part and think itll work. so where do i start? its an old Compaq Presario SR1903WM