DON'T RUN WINDOWS AND BITCOIN YOU WILL EVENTUALLY LOSE YOUR WALLET!!!
Get an external USB 3.0 hard drive for like $50 bucks. Or buy a 32 GB FAST flash card for about the same if you have an sdxc slot (
http://www.amazon.com/SanDisk-Extreme-Class-Memory-SDSDX-032G-AFFP/dp/B007M54E1M/ref=sr_1_3?ie=UTF8&qid=1366473824&sr=8-3&keywords=fast+sdxc )
Download your favorite flavor of linux right from the distro's sight. Format and install on your external hd/flash card. Boot from the external drive and run the os's updater, then install bitcoin.
launch firefox.
1) Go to Tools-->Addons--->plugins and disable java
2) now hit the addons tab and install addon called NoScript.
3)restart FF.
4) before browsing to sites like mtgox, or blockinfo, enter private browsing mode,
5) Got to the bar at the bottom of browser window and click the "S" icon. Make NoScript "Forbid Scripts Globally"
you may need to go back to the S icon and allow certain scripts to make the these sites work correctly. Do so on a one by one basis, and only scripts that come from those sites or have domains you recognize.
6) don't be logged into anything else or have open tabs to other pages when using mt.gox etc. Not even bitcointalk.org
7) log out of mtgox or other online wallets. then exit private browser mode. you can now set noscript back to allowing scripts globally for regular browsing
Don't install additional software on your linux drive. If you must, make sure you get it from the package manager, and that it is a well followed project that is open source and would be highly unlikely to insert attack code. Don't install adobe flash.
**EDIT***
Oh yeah, on linux machines the Firefox plugin to disable java is called iced-tea. you know they rename everything with linux... Java --->Iced Tea. Those C++ Jokers!