Hi Taou,
I came across same scenario while installing a vcenter, however it was damn easy to find the cause.
wait for my next reply and i will collect few info from this blog and you.
These questions seems to be very basic, however proved to be very important
1.what is vcenter version:_____
2. (This is very important ) what is the Operating system and service pack:_____
3. C:drive space:_____
4. No of vCPU :_____
5.Are you installing on the same drive as a base machine O/S drive