Using the common dialog control with the flag of defaultprinter=true is one way. The other is the API...
http://vbnet.mvps.org/index.html?code/system/defaultprinter.htm
http://www.tek-tips.com/faqs.cfm?fid=5479
However, the API seems a bit outdated but checking with MS...
http://support.microsoft.com/kb/266767
http://support.microsoft.com/kb/246772/EN-US/
With Windows NT 4.0 (and earlier versions), you cannot use: Either SetPrinter or SetDefaultPrinter to set the default printer. Either EnumPrinters or GetDefaultPrinter to get the default printer. With Windows NT 4.0, you can use: GetProfileString to get the default printer. WriteProfileString to set the default printer.
So, you will need to check for the os to see if it is NT or earlier or Win2k or later to see which set of API's to use.
Good Luck