Apologies Beata. It's a long time since I wrote that blog and you are correct. However, you should be able to uninstall your current version of CR (back up the keycode). Then download the full SP 4 build:
http://downloads.businessobjects.com/akdlm/crystalreports/crxir2_sp4_full_bld_0-20008684.exe
Install that. Then update that with SP 6 incremental. That should work fine.
Keeping my fingers crossed,
- Ludek