When you plug your BlackBerry into your computer, you should see a BlackBerry icon in My Computer.
If you can't see one, there may be a problem with your computer.
To try to fix the problem:
The removable media drives will either have no drive letter assigned to them, or they'll have a letter assigned which may already be being used by another device. The letter will appear in brackets beside the name of the drive. Right click on the first Removable Media Disk and click Change Drive Letter and Paths
You should now be able to launch the Desktop Software. If you're still having problems you can find more help from BlackBerry.