I have purchased and not possible to download

When you use the Android market, there is a possibility not being approved for the credit card you used. Please Try this method.
Please refer to here for more information about Google Checkout.

the screen may turn black

When updating it with setting the wallpaper, the screen may turn black in the case of OS2.1.You can set it correctly by resetting after setting other live wall papers. It's a feature for OS, and it contains improved OS2.2.

Deleting method of live wallpaper

Please see the following deleting method of live wallpaper.
① Settings>Applications>Manage applications> Selection the contents you want to delete>Uninstall
② Android market>My apps>Uninstall

Regarding a movement between SD card and main body

Some content corresponds to the movement to the SD card.
After moving contents to the SD card, it is likely to return todefault both live wallpapers and widgets after restarting.Please note that here we have the use of mobile phones. Please move the contents to SD card when not in use primarily as a wallpaper. When you display as a widget and the main wall paper, please use it thesaved state in the main body.

It became heavy when updating it

This is caused by the accumulation of cash in the previous version.It improves it when reinstalling it after it uninstalls it.