If you delete one, the other will break.
That is not possible if you are seeing Adobe Reader 9.3.4 & 9.4.1 both the version under Add or Remove Programs.
Once you will update the Adobe Reader, updated files remove the old files and will replaced by newer files. In short Adobe Reader converts from lower to higher version and delete the lower version.
Please check with both the name very clearly whether it is Adobe Acrobat or Adobe Reader. Any how once you will install the newer version, it will detect your computer for any previous version and ask you to uninstall previous version. Starting from Adobe Reader x, it is possible to keep Adobe Reader x with previous version without any crash. Best recommended to remove the older version and be only one version of same product.
However, if you are getting both Adobe Reader 9.3.4 & 9.4.1 under Add or Remove Programs, please do not remove any version, it may cause link break.