Are you sure the applications are 32 bit applications and not 64 bit ones?
Do an antivirus scan. Some viruses can cause this.
Whilst on the antivirus track, try installing the software with the antivirus TEMPORARILY disabled. Occationally anti-viruses see new installations as suspect and wont let them complete.
Sometimes repairing or uninstalling/reinstalling Microsoft office might help with this issue. Try the repair first in case you cant reinstall office after uninstalling it.
Also, if you are trying to install older software, then Windows 7 might not support it - try installing under compatibility mode ...
1) Right-click the installation file and select `Properties'.
2) Click the `Compatibility' tab.
3) Check the box next to `Run this program in compatibility mode for' and select `Windows x' from the drop-down menu Where x is an earlier version of windows)
4) Click `Apply'.
5) Run the installation as normal.
It might also be worth performing a Windows Update as well.