If you want to do a quick one then

Create another table with same structure and insert the rows that you don't want to delete into the other table.

Now truncate the original table .Now the second table has all the rows you want. Now switch the names.

This way you won't block others because you are not performing any big transaction.

I have an article that is worth trying if you want to perform deletes efficiently.

Let me know if you have questions

http://tsqltips.blogspot.com/2012/06/deleting-records-from-sql-table.html