First of all are you an experienced user? Have to know that first.
Do you have good knowledge of Windows support tools and commands?
Do you have a backup PC?
Are you sure that the Windows 2003 ISO is not corrupted?
Which OS were there previously? Was it running Windows?
Have you installed Windows 2003 Properly? I assume that it required the reboot after you have partially installed the OS. Its very important to use a completely separate volume (partition) for Windows 2003. Or a separate Hard drive can be used. Otherwise you will be having problems. It seems to me that your Windows folders have been damaged after the installation.
First run these check lists:
Check your hardware
http://support.dell.com/support/edocs/systems/op330/en/ug/tools.htm#wp1093520
Check whether the Hard drive access light is GREEN
If everything is all right, lets move forward with recovery procedure.
First, if you can see the BSOD message (error description), please let me know. If it reboots before viewing it, after power up the machine use F8 key (tap) until you see the boot options. Chose "Disable automatic restart on a system failure" option.
Include any messages (error desc) in the next reply.
You have to verify that you have no problem with Partition Tables. If you are able to use Windows XP CD/DVD, insert it and go to Recovery console. If you could enter successfully, run command
chkdsk Volume: /f /r
Check for possible errors. F and R find and repair errors and bad sectors (logical).
Check the boot configurations.
Use the command bootcfg (use bootcfg help command to view the help)
You have to configure boot.ini if it contains any misconfiguration.
Guide: Microsoft
If you have configured security for partitions (NTFS security) while using Windows XP, you have to Format those partitions. Windows 2003 will not be able to access them (Access Denied).
Finally if possible check for Hard Drive errors if you have another backup PC. I think its a SATA drive. If you have any third party raid software used, you will be able to restore the system back to normal (or Norton Ghost).
You have mentioned that if you chose Windows XP from the list that the installation will not continue. Thats obvious. That is the purpose of the Boot menu. It will boot Windows XP portion. If you have configured Windows NTFS security for partitions, please restore them back to normal for the partition which you want to install W2K3 server.
Good luck!