Cindi, welcome to the Seven Forums.
Would help to know the model number of that Dell, would make it easier for telling you whether there are drivers/etc available for it. This,
Windows 7 Upgrade Advisor - Download - Microsoft Windows
will help as well.
As for buying it at $199 I'm guessing you're looking at Windows 7 Professional. Unless there are features in Professional that you need I would go with Home Premium instead. It can be had for around $100 or so,
Newegg.com - Microsoft Windows 7 Home Premium SP1 32-bit - Operating Systems
You can see the differences between the versions here,
Compare Windows 7 Editions
and decide which would be the best fit for you.