Can the Dell Studio XPS power supply be replaced with any ATX power supply?
Yes. Dell Studio XPS systems have ATX supply (typically 350W rating). You can replace it with any 350W (or more) ATX power supply from a good manufacturer. Stay away from cheap PSU (power supply unit) manufacturers as they use shortcuts in their electronic circuits. The best thing to do would be take the PSU from your Dell to the computer shop and ask them for an equivalent PSU. Check that manufactuer is reputed and PSU power ratings matches the Dell PSU rating.