I have installed the Canon Digital Photo Professional, which came with the T2i\550d.
Can DPP create an HDR Image from 3 RAW Images? If not, is there a good, free software for that?
If you decide to look elsewhere for HDR software, then this page reviews five free packages. According to them on the easy but less powerful side there is Picturenaut, and on the harder but more feature rich side there is Luminance HDR with the others in between these two.
The only product from their list that I have used is Luminance, and I agree with the reviewer there that it can be a bit intimidating at first. When you are not familiar with the different tone mapping algorithms your only choice is to follow a tutorial (like this one or this one) that gives you recipes to obtain certain looks.
Use Canon's DPP 4.5.0 for the best value (free), and the most in-depth raw editing one can get from Raw and compared with the best Adobe can offer. The work flow is classical, simple, and deeper than any other competitive product, including support for the latest of cameras, lens corrections, and image cleaning from Canon (not compatible with non-Canon). HDR is supported from Raw, as well as Composite tools. Create 3 Raw images using the camera in sequence or take one Raw, export 3 JPEGS of the tone values, and initiate the HDR upload of 3 images. Full range of capabilities allow for incredible tones with black and white, and colors. The only down side is meta-data is removed, and must be replaced after 3 images are merged.