HP / ACER / Dell / Mac
Sadly, it is all a question of taste ... and research. For example, all HP are not the same. The industrial (business) units are built significantly better than the retail units. Our office orders the business units from wholesale and we have been very pleased with price and longevity. At least a 1 year warrenty (parts and ON SITE service) is recommended if you need the unit for work.
If your budget can handle a MacBook with the equivalent specs you will be happier, but you will have a hard time finding "cheap" software for it - they only have a 4% market share. Still, I use my son's MacBook at home frequently and love it for email/web/documents/pictures/spreadsheets.
Be prepared to spend more than double for the Mac if you have to buy software retail.
Acer we have never been happy with. Keyboard, monitor, mother board, it is always something.
Dell is normally great, esp the business units. But they have had quality issues themselves the last year or so. Definately get a full warrenty.
Good luck!