You need to give finance an ROI analysis for the budget ask for new PCs (pre-loaded with the latest software, so you don't have to spend so much time maintaining it), right?

Intel has one for you. Use the PC Refresh Analyzer tool to help determine the optimal refresh and replacement cycle for client PCs.

What it does: provides a sound financial methodology that can help you figure out  (and show the finance dept) optimal PC replacement/upgrade cycle. It includes the Total Cost of Ownership (TCO) modeling spreadsheet tool developed by Intel’s IT Finance group. Associated whitepapers are also part of this extremely extensive solution.

How it’s used: Everyone instinctively knows that holding assets longer saves companies money, but they also know that over time support costs rise and at some point exceed any savings of “sweating” an asset. This solution provides a framework by which to capture and categorize the aggregate PC purchase and support costs. It then models this Total Cost of Ownership (TCO) over various periods of time utilizing Net present Value (NPV) financial modeling techniques.