From what I can tell, the opportunity to sign-up for a Dell Preferred account happens during checkout. Go thru a few of the screens and you'll see it. The problem I'm having is that the details of the offer only seem to apply to SYSTEMS not PDAs. See:
Linky
DimensionTM 2350, 4550 InspironTM 2650C, 2650 or 4150 -- Pay with your Dell Preferred Account $25
DimensionTM 8250 InspironTM 8200 -- Pay with your Dell Preferred Account $50
So, how do you get the $25 to apply to a PDA? It must be for existing preferred account holders. At least that's my theory...
Edit: Here's my cost run-down from Dell's confirmation e-mail (it includes the $40 off and the stackable $35 off coupon from the Home & Home Office catalog plus free shipping credit of $10). I didn't feel like applying for a preferred account after all. Although an extra $25 off would have been nice
Sub-Total $349.00
Discount -$75.00
Shipping $10.00
Shipping Discount -$10.00
Estimated Tax $0.00
Total Price $274.00 before $50 rebate