Problem with Mafia - the patches doesn't want to install

[oldnick587]

Hi everybody!
Would you help me, please, with following problem:
when i'm trying to install patch - 1.1 or 1.2, no matter, which one - I'm receiving the following message:

Registry entry not found!
Mafia is not installed.
Cannot apply patch.

I've tryed to use RegMon to find out which entry is missing, but this is going nowhere and doesn't help at all.
What can I or should I do to fix that stuff and install the patch?

My conf. is AMD2600/ATI9600/512DDR333 under WinXP HE w/SP2.
Thanks very much in advance for your help.
Regards, Nick.