You could try and make avant browser portable because it is already 3MB on my USB drive. You could make it even smaller!
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Avant can never be truely portable. Avant isn't actually a full web browser... it's just a wrapper for Internet Explorer. When you use it, you're just using Internet Explorer's rendering engine and networking. So, even if it were portable, you'd be at the mercy of the local PC. If the PC's Internet Explorer was broken/corrupted, Avant wouldn't work. If the PC's Internet Explorer had spyware, you'd be using a spyware-infected browser. The PC may have IE 5.5, 6 or 7... so your browsing experience would vary greatly from PC to PC.
Usually, you have Avant installed locally. And you know that you need to keep your Internet Explorer up to date, patched and you need realtime spyware and virus protection enabled due to Internet Explorer's numerous security holes. And, since it's your own PC, you can do that. But, if you're moving from PC to PC... you don't have that ability.
Either way... the point is a bit moot. Avant is a commercial product and it's illegal to modify it.
Sometimes, the impossible can become possible, if you're awesome!