Richard,
There are several possibilities as you comment.
My advise is to add a new internal harddisk and use it for Linux, having dual boot. Its quite easy to do it, and then you can run Linux with its real speed (no emulators, etc.).
In my computers I use five different operating systems (in three different harddisks) so I know a little about multiple boots
Open your computer and disconnect the Windows harddisk. Thats the safest option to proceed. Then plug the new harddisk on a different connector (i.e. if you use SATA1 for Windows, use SATA2 for Linux).
Then download Ubuntu (1 CD) and boot from it (live) and it shows an option to install it on the harddisk (its an icon in the desktop). Do it. Once Ubuntu is installed and running, (turn off the computer) go and plug again the Windows harddisk.
Now you can choose to boot from Windows and jump to Linux from Windows boot, or viceversa, boot from Linux and jump to Windows. Both options are fine. I prefer to use Linux boot as it is more friendly.
If your Windows harddisk is the one that you use for development, always do a backup first for security reasons. There will be no risks, but do it, anyhow.