<p>I have the following requirements:</p>

<p>I need a api that works on CE (x86) + .NET Compact Framework to play videos (Similar to CorePlayer API... Just free)?</p>

<p>Is their anything else available or must I use CorePlayer?</p>

DirectShow?
Check out
this page
for a starting point.
Provided that DirectShow is present on your CE, which I don't know...
EDIT
: Since you can use DirectShow, I'd like to add a bit.
As
ctacke
notes, it can be a lot of work if you do everything manually, but it's pretty straightforward if you can use
```
IGraphBuilder
```
(see the sample I linked above).
I don't know much about DirectShow versions, but the one included with Windows Mobile 6.0 lacks a splitter for MPEG audio. It means, e.g., that out of the box it won't play .mp3 files unless you wrap them in RIFF headers.