I am about to install Ubuntu on my PC, byt there is things I would like to know...

I want to istall Ubuntu, but i want to leave also a windows...
If a make 2 partitions on E:/ for Linux, I could see the E:/ from win? (I mean the BIG ONE E:/, not partitions)

And would 500mb for SWAP enough?? I have 512RAM

first of all you wont be able to see E:/ from windows becauuse it wont be called E:/ and it will not be formatted in a way windows can read. Windows uses NTFS and FAT32 while linux would probably be ext2 or ext3. If you want to be able to transfer stuff i would suggest another partition that is FAT32 which can be read by both linux and windows. Second 500 Mb should be fine to start. It depends on what you are doing if it is memory intensive you would want more. It isnt hard to add more though if yous tart getting out of memory errors.
try not to double post. just hit the edit button instead.

But someone said me that I will see E:/ But partitions - NO

What do you mean "I will see E:/ But partitions"?
Unless you format the linux partition in FAT32 windows will not see it, at all, not even see the partition.
You can install a driver for windows that will let windows use ext2/3 (http://www.fs-driver.org/) but without that windows won't be able to even see anything other than FAT32 or NTFS

With that driver I could see E:/ and do everything with files? Delete, move, rename?

/// I need ext2 or ext3 ?

1st ext3 is just ext2 with a journal to help with file system consistency take a look at Wikipedia page, usually ext3 will be installed by default.
2nd The partition will only be called E:/ in windows, drives and partitions are handled differently in linux, everything will be under / (root) so if you install the windows driver then you can use (write, edit, delete ...) ALL the files in the partition. But it wont use the journal so if/when windows crashes there could be some damage to the file system.
Also windows won't be able to use the unix/linux file permissions (so any file can be modified or deleted by anyone logged in to windows) so it's not too secure.

Thank you a lot

I used partition magic to create free space of 20 gb and installed Ubuntu on that for my dual boot with XP.