It won't mess anything up if both are on the system. I had PS6, CS2, PSE3 AND PSE4 loaded on my last computer. I also loved my PSE4 for doing layouts, and only switched to CS2 when I had to make papers and elements for the chats I hosted as a DTM here. Took me quite a few months to save up and buy CS3 when it became available, but as a designer, well i needed it.

I have never heard of a computer coming with such an expensive program loaded on it, so maybe it is just a 30-day trial version? If you are in your comfort zone with PSE4, then stick with it (if it's not broke, don't fix it).

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Colleen in Friendly Manitoba...
Proudly selling digital designs at SBB
(Come take a peek at my Gallery or check my BLOG to see what I'm up to)