OK, so at the end I guess my CD was bad, as it was not completing the ESXi boot.
I was actually using a CDRW that I got from my IT, so when I tried with a regular CDR, it worked all fine.
So, unless other say otherwise, ESXi 3.5 Update 2 works with Dell PowerEdge SC1425.
It did recognize my disks and I was able to configure my datastores.
Folks, thanks a lot for everything.
Thanks and have a good weekend.