"Strike Commander" uses VCPI memory ("Virtual Control Program Interface") a type of "protected" memory. DosBox does not run anything that uses protected mode.
To make matters worse, VCPI memory does not work in any NT OS either (XP). Presently, that means you have three basic options:
1) Run it under a full PC emulator (IE:Virtual PC), in which case you'll probably get terrible performance at a high price (more than $200, demo available).
or
2) Use an actual "old" pc like a 486-66 with an ISA sound card. Often this is easiest as old software was actually made for these kinds of configurations. Useless for programs that need higher specifications.
3) Set up your PC to dual-boot between XP and a DOS-based OS (DOS/Win9x). The best overall solution as you can fall back to the older OS with a reboot for titles that refuse to run properly under NT. This is easy to set up if you haven't installed Win2K or XP. You just make space available for an NT partition, and Win2k/XP will give you the option of a separate install a create a dual-boot menu for you.
Since you already have XP running it's much more of a pain.