[Opserty]

You just need to strip the table tags from the login form in the navbar template. It should give you a form which then works on a single line. Give me a minute or two and I'll try and do it.

Here:

<if condition="!$show['member']">
		<!-- login form -->
		<form action="login.php?do=login" method="post" onsubmit="md5hash(vb_login_password, vb_login_md5password, vb_login_md5password_utf, $show[nopasswordempty])">
			<script type="text/javascript" src="clientscript/vbulletin_md5.js?v=$vboptions[simpleversion]"></script>

			<label for="navbar_username">$vbphrase[username]</label>
				<input type="text" class="bginput" style="font-size: 11px" name="vb_login_username" id="navbar_username" size="10" accesskey="u" tabindex="101" value="$vbphrase[username]" onfocus="if (this.value == '$vbphrase[username]') this.value = '';" />
			<label for="navbar_password">$vbphrase[password]</label>
				<input type="password" class="bginput" style="font-size: 11px" name="vb_login_password" id="navbar_password" size="10" tabindex="102" />
			<label for="cb_cookieuser_navbar">
				<input type="checkbox" name="cookieuser" value="1" tabindex="103" id="cb_cookieuser_navbar" accesskey="c" />$vbphrase[remember_me]</label>
				
			<input type="submit" class="button" value="$vbphrase[log_in]" tabindex="104" title="$vbphrase[enter_username_to_login_or_register]" accesskey="s" />
		
			<input type="hidden" name="s" value="$session[sessionhash]" />
			<input type="hidden" name="do" value="login" />		
			<input type="hidden" name="vb_login_md5password" />
			<input type="hidden" name="vb_login_md5password_utf" />
		</form>
		<!-- / login form -->
	</if>

Its not tested so I'd try without the conditional first just to be safe then you can use the conditional after if it comes out OK. It may be better to remove the checkbox and remember me phrase to make it look more like the image you posted.