An InformationWeek article which says that half of current corporate PCs probably wouldn't be able to run Vista, Microsoft's new operating system, if it were released today:

Assuming Microsoft does not suffer another delay, the cutoff point would be computers bought in 2006 or earlier. Gartner advises companies to replace notebooks every three years and desktops every four years. Given that most companies will take at least 18 months from the time Vista ships for planning and testing, by the time those organizations are ready to deploy the new OS, the useful life left on 2006 PCs would be about 17 percent on laptops and 37.5 percent on notebooks.

Among the major requirements of Vista, compared with Windows XP or 2000, is a graphics card that supports Vista's user interface and visual enhancements, which include translucent window frames and task bar, real-time thumbnail previews and task switching, enhanced transitional effects and animations. While these features within Aero won't be important for many companies, other improvements in the UI will, such as better window stability, smoother screen drawing and interface scaling.

In addition, computers will need at least 1GB of RAM to run Vista, and an additional 512MB if companies plan to use PC virtualization during the migration to run an older OS and Vista simultaneously, Gartner said, just upgrading RAM on a PC costs from $100 to $200 per machine for many companies.

This finding doesn't surprise me all that much considering that as of a year ago, many corporations appeared to still be running Windows 2000 on a lot of machines.

...via Digg