Failure when installing Slides

I cannot install the slides extension to SSRS using the latest msi download. Every time I try it stops with a message saying that a more recent version has been detected as installed. However I know that I have NEVER installed this product, even as an evaluation, so why does this message appear. I have installed all the other SSRS extensions without a problem

Any ideas?

Dear alifin,

Thanks for considering Aspose.Slides for RS.

Probably, this is because of automatic installation, you should try manual installation.

That fixed it, thanks