I don't know why people just like discouraging others by simply telling them "you can't do it" when they don't even know what they are talking about. If you don't know the right answer, why try giving one?
The UM100 CAN be installed in any 64 bit system. You just have to go and update the driver manually once it's installed. Here's what I did to make it work.
1.Double-click the quicklinkmobile.exe application from cricket. It will unpack a folder with the installation files in the same folder the quicklinkmobile.exe app is residing.
2.Go in that folder and click on start.exe, then click on install quick link mobile. Go through the normal setup as you normally would.
3.Once it finishes installing, connect your UM100 UTStarcom modem on a free USB Port. Don't open the Cricket Wireless application just yet.
4. Go to start menu, right click on Computer and select properties. Then click on device manager on the left. You will find the UM100 modem has an exclamation point on it.
5.Right click it and select update driver. Select "Browse my computer for driver" Option at the bottom. Click on Browse to select a driver from a location, then navigate to your root drive (usually C: and sometimes D

then to Program Files (x86)/Cricket/Quick Link Mobile/System
6.Make sure you navigate to this cricket wireless installation folder. It should be in C:\Program Files (x86)\Cricket\QuickLink Mobile\System. Once you find it click ok. Make sure "Include subfolders" is selected under it. Click on "next" and now it will install the driver.
7. After it installs, it will create two more Unknown devices with exclamation points. Wait a couple of minutes for the system to finish up installing that one before you continue with this instructions.
8. Now repeat steps 5 and 6 above for each of the two unknown devices until there are no more devices with exclamation points in device manager.
9. Now open Up Cricket Wireless application on your desktop or start menu, and continue with the normal modem activation of the wizard that appears. That's it! It will now detect the modem and activate it. Allowing you to use it.
10. Go and find whoever said you couldn't use this modem on 64-bit systems and punch them in the face.
11. Call me so I can punch them in the face again.
12. Enjoy your newly installed UTStarcom UM100 cricket modem on your 64 bit system. Ask Cricket to update their website with this information. Punch them in the face too for the sake of completeness.