Vanishing Files - Dual Boot without partition the cause?

[noexperiencenecessary]

Help! I just instantly lost EVERYTHING from my Windows XP Pro side of my hard drive while on the net on the Ubuntu 9.04 side of the dual operating system I put on my laptop about 2 months ago. Every single bit of saved material from Windows disappeared including my photos, music downloads, saved material from the internet, files for work and most disasterously, my half-finished 2008 income tax return. The page I was on froze up and wouldn't unstick, so I rebooted, then discovered what had occurred. TurboTax, Google Earth and my virus programs were untouched, but my tax files vanished and the internet and virus programs had to be updated. It took me back to what the laptop looked like the day I got it (2 months ago) and even greeted me with the "Welcome to XP Pro" message. Nothing from the Ubunu side was lost. I had installed the Ubuntu to do a dual system boot up as I need Explorer for some functions we use at work. I didn't put a partition in the main drive as I did not know how to do this. I downloaded the Ubuntu off the net and am not so technically saavy as to know how to do partitioning without much risk and mental agony. Does anyone know if my disappearing Windows files could be due to the lack of a partition? Anyone know if my missing files might be recovered somehow? I lost a whole back up drive worth of material while in New Zealand and some guy at work found them all. Perhaps I will be lucky again. The Properties feature in My Computer is telling me I have used up 22gb, so maybe they are hiding somewhere. I tried System Restore and took the computer back two days, but nothing happened. I fear I was hacked or have a nasty virus, so I wrote also to the seller of the laptop as well as the Kaspersky Internet Security people to get their take on my problem. Would I be better off to merely have a bootable flash drive with Ubuntu on it and save my files onto it, or would putting a partition in my hard drive solve the problem? Would there be a novice-friendly utility to help me partition my hard drive if I bought a commercially made Ubuntu disk? If I didn't have to use Explorer for work I would go entirely Ubuntu. Until I find out the cause of my disappearing files, I have reverted back to my old Windows-only laptop. Can anyone help me?

Another question I have is does having a more unusual or simple version of Linux (like Puppy, Damned Small, Feather, etc) decrease the likelihood of being hacked or experiencing viruses? Are these variant forms of Linux just as functional and full-featured as Ubuntu is? If I am going to make a change to fix whatever I did wrong above, this would be a good time to do it.

Thank you all for your help. I live in Glens Falls in case anyone is wondering.