Re. "side note" Multiple OS/s on separate HDDs is a much better setup, no messing about with Boot loaders, is safer, because if you loose a drive with with partitions, you loose everything. I have done it with 98SE, XP, Linux. The little bit of time selecting the OS to boot from never bothered me.
Until you have decided on virus protection, first use Windows Defender, > http://res2.windows....8ebadc364_0.wmv
If this makes sense, consider doing the following.
Your 2TB as an OS disc is huge, you may get degraded performance as files will be spread out over the whole disc, Ensure only the OS disc is connected. At install, I would create a 500GB boot partition, leaving the rest as unallocated.
install 8.1 OS, MB driver/utilities (decline free or trial software) update the OS, create recovery media, install software, (except Sound Blaster) test. Then, when satisfied.
Disconnect the C/ drive, connect the 250GB drive, change the drive letter to E/, Install XP, (if you are connected to the internet, LAN drivers should be installed and Windows generic drivers.) Update the OS. use the default Firewall, install Avast antivirus, test.
Use the Dell installation disc to install SB software, use the Dell Driver disc for the SB drivers, test to see if it work. if not, I may have a solution.
Reconnect the C/ drive and configure the boot priority.