According to the State Election Boards Website you have until April 11th to to register to vote in the May 6th primary:
2008 Primary Election
Last day to register to vote: Apr. 11
Absentee Voting: Mar. 17 - Apr. 29
One Stop Absentee Voting: Apr. 17 - May 3
Here’s some pertinent information on registering in N.C. fom N.C. Politics.com. More information can be found at http://www.nc-politics.com/vguide.htm:
Where Can I Register to Vote?
You can register to vote, make change to your registration or obtain a mail-in registration form at the County Board of Elections Office in the county you intend to vote within. Additionally (in some counties, but not all) at:
* A public library,
* The Department of Motor Vehicles,
* Some Public Agencies,
* On the internet
Forms may be submitted by facsimile transmission, as long as a permanent copy of the completed, signed form is delivered to the county board no later than 20 days before the election.
When Do I Need to Register?
* If mailed, the registration form must be postmarked at least 25 days prior to the election
* If hand delivered or faxed, the registration form must be received no later than 5:00PM on the 25th day prior to the election.
Do I Have to Declare a Party?
Party affiliation determines the primary in which a voter is eligible to vote. You may register with the Democrat, Republican or Libertarian parties, or you may register as unaffiliated. Unaffiliated voters may vote in a party primary if authorized by that party. If you do not declare a party you will be registered as unaffiliated.
Do I Have to Contact the Board of Elections if I Want to Change My Registration Information?
Yes, if You:
* Have moved within the County since you registered in the County (it is a violation of state law to return to your old precinct and vote if you have moved more than 30 days)
* Have changed your name
* Want to change your party affiliation
Go here for online application form