I have installed Wubi (Ubuntu 10.10) recently. It takes more time to boot than Windows. But my main concern is that my browsing speed is much slower compared to that on Windows 7. How can this be resolved?
This can't be (totally) resolved. Wubi means you run Linux on "NTFS", it's just not for desktop use. Wubi is there for people who want to try Linux/Ubuntu.
The browsing speed I guess will be the cache. Here is an article how to speed up this. It'll use more memory, but it'll render faster.
However.. and I'm really honest here, on Windows pages get rendered much faster FOR ME (notice the FOR ME part!). I have tried many distributions and still using Linux on some of my PCs but no. You could say its all about the openGL and stuff which will come with Firefox 4 ..but no. It's always been snappier.
Also, we talk about your browser render here. What about your network driver? That's the other suspect. Video driver? What VGA you've got?