VBox replacing Terminal Server?

[arvirago]

Hi, I'm new here.
I have a machine running Windows Server with Terminal Server, and a few (about 20) clients using Windows XP and connecting to this Terminal Server to execute some corporate software.
I thought about trying to replace this with a Linux server. I have installed (in a new machine for testing) Ubuntu Server 8.10 with VirtualBox. I have created a vm with the VBoxHeadless and then connect to it from a XP client (using remote desktop) and install Windows XP on it. Everything goes fine, except the mouse. When I connect to the vm I get two mouse pointers, the local one (which moves fast but it's of no use) and the remote one (which moves slowly and laggy, even if using the keyboard goes really fast).
¿is there an easy way to fix this?

OK, now let's say I get this vm up and running my software. What would be the best approach to get those 20+ PCs connected? I thought of:

1- Have 20 virtual machines running, each with its own virtual disk, and configure them with different ports or different IP adressess so each PC can connect through remote desktop directly to its own vm.
2- Having the same 20 vm running but with the same virtual disk, ¿is it possible? If not I would have to give each of the 20 disks no more than 10Gb.
3- Having the XP client to the linux server (not the vm) and then run a vm for him. I guess this would need xwindows on the linux server.

Once I have the testing vm with all the software installed and correctly running, can I replicate this virtual hard disk for other vms or do I have to manually install everything again and again?

Sorry if these are newbie questions

[arvirago]

OK, I was able to fix the problem with the mouse, installing the Guest Additions.

¿No one knows about having multiple virtual machines sharing disk or creating them on the fly, so I can emulate the Terminal Server environment?

[vbox4me2]

In terms of technology you can't replace TS like this, you can run multiple XP Guests provided you have enough ram and cpu. Make a single template, set it to immutable and clone it to how many XP licenses you have.