I have 2 ifp-895 and 1 ifp-899 (and an H10-20Gig). I have seen some behavior like this if Windows Media Player or another tool (like winamp) is running. It behaves like Windows Media Player locks the driver. You have probably closed all applications before you submitted this issue but I thought I would post it. I have XP up to date on 2 machines with IMM working fine. When WMP is closed, IMM usually immediately sees the ifp device.
As an alternative to IRiver Music Manager, I have used Total Commander:
Total Commander - home
with the iriver plugin:
Iriver Storage 2.2b - Total Commander
You install Total Commander, unpack the iriver plugin (iplug22b.wfx is extracted) and point total commander to use it via Configuration->Options->Plugins->File System Plugins
and add iplug22b.wfx to it.
This is like IMM in which you have 2 window panes: source + dest.
So on the source side, you would pick c:\my_music
And on the dest side you would like to pick the iriver player, which is a little trick
or non-intuitive:
To pick the ifp-895, it is under the drive letter drop-down control: which lists c:,d:,...Network Neighborhood.
Under Network Neighborhood, you should see Iriver Storage if your plug-in is added (even
if your iriver player is not physically connected).
A huge benefit of this tool is that it allows you to copy (mp3, wma, ogg) files from dest. to source that the IMM does not.
Before finding this tool, I was using dos to rename *.mp3 to *.rec (which the Iriver 895 will
play) and then you can use IMM to copy from dest. to source.