Mitch, depending on your computers speed, amount of available RAM, and the applications you have running, your browser can take awhile to open. Why don't you tell us your configuration first.
As far as USB flash drives, there are tons of good ones out there. I have had good luck with Sandisk.
Asking which is the most popular motherboard on the market is like asking which is the most popular car. Depends on what you are looking for. Right now, unless you like to tinker and are planning to upgrade components alot, there is no reason to build your own. Companies like Dell are offering systems with 17" LCD monitors for $420, and these are P4s with Hyper theading and DDR2 RAM. So if you want to upgrade, go that route. I don't have the link to the special deal that Dell was having, but I have it on my other machine and I can post it if you like.
