[JWait]

I'm not sure what it is you are trying to do. You have a "Your Account" box which appears on almost every page on your site, which seems to defeat what you say you are trying to do. If you moved this and simply used a button that said "login" which you could place almost anywhere (I would put it in the header under you language "bubbles") and have it link to a "Your Account" section displayed in the main part (center) of your page. You could also have "login" change to "logout" once a customer has logged in, or even say "Your Account" and take them to a page (again, in the center area) that allows them to modify or delete their account, and check order history (all default x-cart options).

I don't think "create account" should be enabled by default, but here is the code to do the same thing for newsletter subscription, just use the same logic for your checkbox'...

FIND:
<td><input type="checkbox" name="subscription[{$listid}]" {if $subscription[$listid] ne ""}checked />{/if}</td>

REPLACE WITH:
<td><input type="checkbox" name="subscription[{$listid}]" {if $subscription[$listid] ne ""}{/if}checked /></td>

I moved the closing {/if} to BEFORE the checked. This preserves the logic... and auto-checks the box for new registrants and maintains the status for existing.

the ONLY downside that I see here is that if the customer modifies their profile, and the user had previously unchecked the box on the modify profile page, it will now be checked... nudge, nudge... "please sign up for our newsletter".

Also, I would change the text "The form below allows you to create a profile which is necessary to place orders. Do not forget that this information is essential to use our services correctly." to something that doesn't say "create a profile", maybe something like "The following information is necessary to process and ship your order..", in fact I usually avoid the term "profile" altogether, replacing it with "account" wherever it occurs.