Greens' above solution originally posted by Niket proved to be a boon to me.
I took the FWP LSP-340e a few weeks back. Even though I could instal & connect to internet thro' Win98se, all my efforts to instal & connect thro' winxp sp1 (dual os) failed.
I used to connect to the net with my earlier 56Kbps modem using 98se and hence winxp was not updated. Everytime it was "failed to instal modem" (even the standard 19200 kbps modem).
Being a small time techie myself, I scourged the net for possible solutions until yesterday when I struck gold at RIM discussion forum. The solution turned out to be keeping your XP up to date and maybe the RPC problem as indicated elsewhere in this forum. It was not a 'problem with your cable', 'problem with the driver', re-instal xp etc advice I got from different sources.
After installing the said three files, I could instal the modem with the 2 MB "rconnect_lg_lsp_340e_com.zip" file found in a filemirrors search (not the 7 MB file at rim site) as clean as a whistle.
Thank you niket and greens.