There are frequent cries for help from Umax users and the usual recommendations lead to pay-for sites like Driverguide. I can understand why this arises because have tried looking for a 4100 download on Umax's own sites without obvious luck and one mentioned buying a CD with drivers on it -- I clicked on a UK site and ended up on a German one.
Frankly, if this is an older model, you might be better off downloading a commercial program like Vuescan or Silverfast.
Alternatively, I'd consider dumping the Umax and avoid the brand in future -- my experiences with Epson's drivers have not been great but I've always got there in the end and their staff were quite helpful. Canon, presumably, are also decent to deal with based on my experiences with their printers and 35mm cameras.
Choose one of those brands and leave the cheapies alone.