Dell Inc. may lose more ground to rival Hewlett-Packard Co. before it generates enough services business to regain its spot as the No. 1 personal computer maker in the United States.

During the first quarter, Round Rock-based Dell lost that spot to California-based HP for the first time since 2001. The turnabout happened because Dell’s U.S. shipments decreased 16 percent while HP’s increased 11 percent during the quarter, industry research firms reported.

Dell’s slow retail store sales combined with a recession-induced slowdown in sales to business customers contributed to the ranking change. Also, Dell has been slower out of the gate with the very popular low-priced netbooks, while competitors HP (NYSE: HPQ) and Acer sell huge quantities of them, said Mikako Kitagawa, principal analyst for Gartner Inc.

And since business customers, which include government and educational clients, account for 60 percent of Dell’s U.S. market, the economic downturn’s effect was heightened, she said.