Uninstalling / Installing PSP7 & 8 (HELP !!)

Here is my problem :

I am running under Win98.
I had PSP 7.04 installed. I unstalled it (mistake !) to make room for PSP8.
I installed PSP 8.03 (trial version).
I was not very happy with the new interface and the bugs so I unstalled it
and wanted to revert to PSP 7.04.

But now the installer stops quickly with a message such as "You have a
version of this product already installed. Uninstall it first using
add/remove ....".
I noticed in the registry that there are many "traces" of the Jasc software
left, despite my use of RegCleaner.

What should I do in order to be able to install PSP again ?

Thanks in advance.

--
Gilles Garrigues

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