Firstly look at the Frequently asked questions on the Ulead website
http://phpbb.ulead.com.tw/EN/viewtopic.php?t=11923
There is a section dealing with installation problems.
Free up space on your C drive by deleting temporary files.
Check the System Restore settings, the default setting is 10% of the size of your hard drive which is normally excessive, either reduce it to a smaller amount or turn it off altogether.
Check the size and location of your internet explorer webcache, again this might be too large and eating up drive space.
Delete any old and unused programs (via the windows control panel) It can be suprising how many programs get downloaded off the internet especially if you have youngsters who have access to your machine.
Steve J