Avid to Encore Problems

Hey guys, in a bit of trouble here, would appreciate some help. Long story cut short, had a friends Mac for a couple weeks to edit a film on. I was using Avid and exported the file as a Quicktime file, under the Avid DNxHD Codec. Expecting problems to arise I also used Handbrake and various other encoders to create different versions, so I've got various MPEG2/MPEGDVD/H264 files sat on my PC now (the Mac is gone)

I wanted to put the QT file into Encore, but when I did I got the message:

Quicktime and/or appropriate codecs do not appear to be installed.

No problem I thought, I'll just try out the various converted versions and see which looks best. They go onto DVDs fine, look good for a down conversion from HD to SD, but there is interlacing problems on the some of clips. I think it must be Encore, but going back to the original files and playing them on the computer - same problem. Doesn't look I clicked deinterlace in Handbrake, etc.!

My PC isn't super-power and I don't want to get bogged down in more conversions if I can help it. Is there anyway I can get the main QT file into Encore? I really need help here, deadline is in two days, everything else is ready to go.