You don't have to reformat if you don't want to. Some just do it to get rid of "bloatware" which is just extra drivers and programs (Usually Trial versions) that they don't want on their computers.
You can use your computer right out of the box with dell. You may want to remove some of the trial programs and other things that you definitely wont use just to free up space but other than that just go ahead and install your stuff.
A great way to keep the computer running great is to set a schedule for maintinance. Like do a virus scan, spyware scan, disk cleanup, and disk defrag about once a month. This is to insure top performance and reliability. I also use a registry scanner called Registry mechanic to make sure the registry is running well. The registry scanner is not required but the others mentioned are important for optimal performance. If you are running on a tight budget you can get free anti-virus and anti-spyware tools. AVG Anti-virus at www.grisoft.com
and Ad-aware at www.lavasoft.de
. These are running great for me and as long as you keep on top of them will get the job done on a tight budget. Also Norton has System works and Anti-virus free with rebates if you prefer something with a name behind it along with support. Norton is always reliable with their removal tools.
Other than protection make sure your windows is always up to date and you should have no problems and should have a reliable machine for years to come. Congratulations on the Dell Dude!!!!