If the drivers are not there for that model laptop, you will need to find it yourself.

I'm not sure why on earth you would want to install 2003 on this laptop.  There is a good chance it won't work reliably - or at all.  If you need 2003 for something, you should be installing it as a virtual machine.  Why do you need 2003 on here?

If you want to try ... try the 7x86 drivers - it has a textsetup.oem file in it for use with XP (and 2003):

http://www.dell.com/support/drivers/us/en/19/DriverDetails/Product/vostro-2520?driverId=2FYW4&osCode=W732&fileId=3176091816&languageCode=EN&categoryId=SA

Without a floppy drive, you will need to use nLiteOS.com (or unattend.xml) to integrate/slipstream the drivers into the installation media.

If that doesn't work, just boot to BIOS and change SATA Operation to ATA/Compatibility, since you probably won't find a more suitable driver.