I have installed ubuntu 10.10 on my laptop using wubi. My laptop also has vista installed. Would it be possible to somehow run ubuntu (virtually?) while windows is running without having to restart the laptop?
Yes, this is possible. VirtualBox can virtualize an operating system that already exists on a physical partition.
However, this is not recommended. When you installed Ubuntu, it configured everything based on the hardware it found during installation. When you load it in the VM, it will find all sorts of other hardware and may need massive reconfiguration.
That being said, you can find a tutorial that does something very similar to what you are trying to do here: http://www.neowin.net/forum/topic/784138-howto-boot-existing-ubuntu-partition-using-virtualbox-inside-windows/
I don't believe You would be able doing this using wubi alone. You need to install a virtual system like virtualbox and then you could create an Ubuntu vm in it. You wouldn't use wubi though, but rather a usual Ubuntu iso.
http://www.psychocats.net/ubuntu/virtualbox has instructions how to do this.