Grand news for Dell (Nasdaq: DELL) investors: According to two of the world's leading tech trackers, the company's expanding its lead in the PC race -- at least in the U.S.

According to research firms IDC and Gartner, Dell grew its PC shipments 17% in Q4 2007. The build-to-order computer maker still ranks No. 2 worldwide, behind archrival Hewlett-Packard (NYSE: HPQ), but it's ahead of Acer, Lenovo, and Apple (Nasdaq: AAPL) (in that order) in market share.

Why is Dell doing so much better here than there? I suspect the firm's much-publicized tie-ups with Wal-Mart (NYSE: WMT) and Best Buy (NYSE: BBY) had something to do with it (the former more than the latter, which was only announced in December.)

Happy as the news appears, however, Foolish investors shouldn't put too much faith in sheer market-share stats. After all, Dell shares have already fallen plenty, even when the company was No. 1 worldwide.

In addition, we've always liked that however many computers Dell sold, the company's build-to-order business model meant it never had to tie up a lot of cash in inventory sitting on store shelves. That model is changing now.

Is change good?
While the market-share stats may tell us that change is for the better, what matters most to investors is learning whether change will turn out worse for Dell's free cash flow. For news on that score, make sure to tune back in to in February, as we examine Dell's fiscal 2008 Q4 and full-year earnings report.

How swell is Dell? At Motley Fool CAPS, investors like you give the firm just two stars out of a possible five.

Meanwhile, two entirely separate Fool newsletters -- Motley Fool Stock Advisor and Motley Fool Inside Value -- have recommended the stock. Grab yourself a free trial to either one (or both!) and find out why.

Fool contributor Rich Smith does not own shares of any company named above. Both Best Buy and Wal-Mart are Motley Fool Inside Value selections. Best Buy is also a Stock Advisor pick. Dude, you're getting The Motley Fool's disclosure policy!