Dual-Boot: 1. Windows XP without Internet; 2. Linux with Internet

[GB-UK]

My proven, reliable steady steed Win XP is used for all my personal data. Obviously, I use this on a PC without an Internet access. Another PC, using Linux (Ubuntu) has Internet access.
Is it possible to run both these operating systems, BUT STILL maintaining the security of my personal data under Windows XP?
i.e.
When Linux is used, could any third party gain access to my personal data used with Windows XP?
-->> The same external HDD would be used for personal data.
-->> Internal HDD for Dual-Boot.
.
I wish to move from two PCs to a single PC.

[DaveLembke]

Linux is more secure than XP. As long as your dont install something bad and always get updates then your secure for Linux and no one can access your data but yourself.

[BC_Programmer]

If you want you can disable your network drivers within the XP installation so that it cannot access the Internet at all.