For unknown reason, my partition magic 8 installation didn't go to completion (script error). Yet, programs group was still added to Start->All Programs menu. I wanted to uninstall PM8 but I couldn't find uninstall program option under Start->All Programs->Partition Magic group. I checked from ftp://ftp.symantec.com/public/english_us_canada/products/pmagic/pmagic_8/manuals/PM8.PDF mentioned below instructions available to uninstall PM8

Uninstalling PartitionMagic
1 On the Windows taskbar, click Start -> Settings -> Control Panel
2 Double-click Add/Remove Programs, then select PartitionMagic 8.0
3 Click Add/Remove

But PM8 was not find from list of installed programs.

Please tell how could I remove this incompletely installed application cleanly besides just deleting the program directory under \Program Files ?

try using cccleaner tools.