While we were looking at the Dell problems with Vista and FireGL cards, something leaped out at us. Red Hat offerings are notably cheaper than MS products. Now, you might say "well duh!" but this is not the free downloaded version, it is a fully-supported, packaged copy with media.
You can see the difference by going to the Precision page here and clicking on Red Hat, XP, and Vista variants of the same box. Most of the time, companies make it hard to compare directly by changing hardware enough to stop direct matching, but not here.
If you set the hardware all the same, you will come up with a Redhat version for $1952, and XP or Vista will set you back $2011. This sets the Vole tax at $59 over Red Hat, but unless Red Hat is willing to talk Dell contracts, we can't be sure how much a Windows licence really costs. µ