We've been using the Dell D620 and D630s at the office and they are solid. The sales people all have them to demo our product. We have 13 of them out in the field and I've set up every one of them.
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We can still get them downgraded to XP Pro from Dell :teehee
D630 would be my choice.
Get the good warranty with it. You could throw it at a tree if you get mad and Dell will replace the whole thing next day, no questions asked.