What would cause a loud squealing under the hood only at startup?

What is your question?

I looked at the drive belt, and it looks good. I recently put in another engine and assumed the belts were changed out but I'm not sure. Should I take off the belt and inspect it thoroughly or is there something else wrong? I have been driving this car since 2009 and have made the usual repairs so I would appreciate any info you can give me. This noise only began about 2 weeks ago but is quite embarrassing when starting it in the morning.

What makes this problem better or worse?

Cold engine. First start-up in the morning.

How long has your 2001 Hyundai Accent had this problem?

Maybe two weeks now.