http://www.mandrakelinux.com/en/hardware.php3 <- to check Supported hardware.. But I know the database is just not enough up-to-date.
You should try, and you will know
I think everything will be ok (after some difficult efforts maybe, but I'm sure it will run)
Plug it, check if you got it with usbview or something (you probably need to install it)
Mandrake Control Center > Material is a good diagnostic solution also. and last but not least, the very last one is surely the best solution (every solutions is in fact if nothing show up when you plug your modem, but something should in newest mandrake10.1).
So if its not, launch a terminal, plug your usb modem, and check with dmesg (as root) if you get an USB reaction and detection of a new device in the last lines..
This is just to be sure that your Modem is well known. many devices are not well recognize because there is no driver at all for them.
If everything is ok, with Mandrake 10.1, you should plug-in the modem, configure the login/passwd (like in a common Windows 2000/XP) and you are done. But if you got difficulties, here is a start of tracing the future possible problem.
Hope someone could tell you "Yes, I use it, and I works" :-)