Capital costs - the hardware, the software, and upgrades to both.

Servers, networks and printers - the more computers you have the more you need.

System administration - the number of sys admin staff depends on the type of machines and type of applications.

Hardware maintenance - maintenance companies charge more for critical support and quick response times.

Software support - should be quickly available, preferably for local-rate or free phone calls.

Productivity costs - includes training needs, time and work lost due to crashes, and even time spent asking other colleagues how to do things. Hard to measure.

Electricity - Some screensavers can switch monitors off, saving power.

Storage - IT equipment often requires extra office space.