I noticed when installing libreoffice 3.3.2 (my first with Libreoffice) on top
of OpenOffice.org (GOoo actually 3.2) that Open With and Search for programme features could not find LibreOffice components, such as swriter etc. 

I discovered that the paths in the registry were not updated by the LibreOffice installer. I manually edited all OpenOffice and Sun Office entries in the registry (regedit) to point to the Program Files\LibreOffice 3\  directory, and I was thereafter able to find swriter, scalc etc in "Open with" after a right click. Double clicking on odt files then also started working. My windows version is some build of XP SP3.

After installing Libreoffice 3.4.3  to upgrade from LibreOffice 3.3.2 (LibO_3.4.3Win_x86_install_multi.exe) I found that now references to the \LibreOffice 3\ path had not been changed to \LibreOffice 3.4\ which was the new directory in \Program Files\. This time I tried a different manual fix. I copied all the file/directories from \LibreOffice 3.4\ this time to the still extant but almost empty \LibreOffice 3\ directory .. and once again things began to work again, although when starting LibreOffice, a message showed some options/features to be disabled. In the directory setup (within sOffice) I found only \LibreOffice 3\ directory references. [All shortcuts in the "start"/"programs" menu also needed to be changed manually, of course.]

My next workaround will be to install to the (old) directory path \LibreOffice 3\ rather than let the installer choose its own (new) path.

I thus speculate (reason?) that the cause of this bug (in Windows) may
partially lie with the installer not correctly building or updating registry
entries if a previous version of (Sun-?) Open- or LibreOffice exists.

If this problem is repeated for other users' installations it would be a blocker to moving to full use of LibreOffice from MSOffice etc. and is a frustration for old users, as previously set file extension associations fail.

Max