I've installed two systems:window xp and ubuntu.
vmware is installed in windows.
Is it possible to enter
vmware,while of course I'm still in windows?
Wow, your question is like a puzzle - trying to untangle the seemingly random combination of letters into a series of sentences.
It looks like you have installed some version of VMWare (Workstation, Server, Player - which one? which version) installed on top of some version of Windows. The Windows machine may also have a copy of Ubuntu installed on the same disk allowing selection via GRUB - is that right?
If that's right then you can run Ubuntu from it's own partition but it's reasonably hard to do. THID is a link to a guide on how to get a local Windows partition to run as a VM, the principal is the same but varies obviously, it's the best guide I've come across.
If I've misunderstood your question then I'm afraid you're going to have to rewrite it to make it clear.
I think you're asking if it's possible to give direct disk access to a "VM" in VMware that happens to already be a "real" install?
If that's the case, then I do not believe it's possible.