Here are the instructions for installing X1 (through update "D"):
http://www.cakewalk.com/support/kb/reader.aspx/2007013277?DL=Instructions I would do it like this:
**Temporarily disable your internet connection, and also the realtime scanning of your antivirus. (I'd consider this an optional step, as I've never had to do it, but some folks have run into problems by not doing it, so it bears mentioning).
1) Do a clean uninstall of X1 (including manual delete of leftover folders and registry keys).
2) Re-download all of the updates using a download manager.
3) Install (with "Run as Administrator") from X1 disc, then updates, as outlined in the instructions. Reboot your system.
**If you disabled the antivirus, don't forget to turn it back on!
Good luck!