tom92909 is correct, the install should not take that long.
along with clearing the DW cache file, it may also be anti virus or other real time file scanning software that is causing the install to take a long time.
If you have software that scans files as they are created, it will make the install take quite a bit to finish.
If you are on a windows system, try running the disk clean up tool under S†tart -> Accessories -> System Tools -> Disk Cleanup and select the options for Empty the Recycle Bin and Remove Windows temporary files. having lots of files in the recycle bin or the windows temp folder will effect both install an uninstall times.