If you have the game installed on another drive than It'll be in a different directory and you can't run SWBF1 maps on SWBF2 (or the other way around). The two game files are setup differently. The only way to get them to work is with the SWBF2 Mod Tools but you still need all the source files for that map and when I say source files I mean all the files that are put together into the LVL files. There are the shipped SWBF1 maps converted to SWBF2 though, that is what you want right? Since this is the SWBF2 section. The SWBF Conversion Pack
is a mod that converts the SWBF1 shipped maps to SWBF2 with a lot of additional features. The latest version of the mod is here - SWBF Conversion Pack (1.9)
and the final version will be released in a month.
This mod is still a WIP (Working in Progress) so it will still have bugs in it.