Thanks for a reply, Carlos.

I tried to follow your way, and I thought I got it working, but I get different errors now.
Maybe I compiled it wrong or something so I want to give it a few more try, but my supervisor really wants me to ask on the forum about this.
So here it goes.

I installed Qt and Qt Creator, and compiled qwt too. But I still can't find qwt designer plugins and when I check the list of the plugins, I see qwt designer plugins under Failed Plugins.
It says it "Cannot load library C:/Qt/4.6.3/plugins/designer/qwt_designer_plugin5.dll: The specified module could not be found."
Also, when I try to run the qwt examples, it builds okay but I get "C:\qwt-5.2.1\examples\bin\simple.exe exited with code -1073741515" this and it just exits.
So I'm assuming I did something wrong when I installed qwt..

I'm going to keep working on this but I also want to hear from you too.
Thank you very much!