T-SQL Performance Issue when deleting large data

Hi all,

I've a problem when deleting 1.2 millions of 7.3 millions row. it takes very long time.file size is 16gb.
working on intel xeon 2.0GHz (4 cpus) and 4 GB of RAM.

The SQL syntax is :

DELETE Material WHERE MatCode Like 'E9AAAA%'

Table Structure :

CREATE TABLE [dbo].[Material](
[MatId] [int] IDENTITY(1,1) NOT NULL,
[GroupId] [int] NULL,
[MatCode] [nchar](20) NULL,
[MatDescr] [nvarchar](300) NULL,
[UOM] [char](10) NULL,
[InputBy] [nchar](36) NULL,
[InputDt] [smalldatetime] NULL,
[UpdateBy] [nchar](36) NULL,
[UpdateDate] [smalldatetime] NULL,
CONSTRAINT [PK_Material] PRIMARY KEY CLUSTERED
(
[MatId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]


when i saw on task manager, it's only takes small resources, under 10% processor usage (1 cpu working and others relatively idle) and only 1.6gb memory.

can anyone help me how to optimize it ?

Thanks.
fokeman