Help! I stuffed up my Virtuemart import

Hi there,
I'm using J! 1.7 and VM 1+
I did the import ok but I skipped a couple of pages because I was playing with my mouse (sorry)
So it imported everything expect the prices and images
So I went to do another import and it didn't import anything else because there were no new products
In all my wisdom, I deleted all the products thinking it will re-import them but it doesn't
I even uninstalled Hikashop and reinstalled it but it still thinks I've already done the import

Is there a way to re-do another import please?
It must flag the items somewhere to say they have been imported. Can this flag be removed?

thanks a lot and sorry for my mistakes

Cass

Thank you so much nicolas!
It worked perfectly!
And I copied the images into the upload folder so now everything is working like a charm
Thank you for your prompt reply!