Hi Narasimhan,
You have to increase data file ( device ) size using resize command.
1>sp_helpdevice
2>go
Try the above command and check the data file size.
1>use master
2>go
3>DISK RESIZE name = '<device name', size = '2048M'
4>go
5>alter database <SID> log on <device name> = "2048M"
6>go
Thanks
Siva