problema con rowspan

[fabio.battaglia]

Salve a tutti, ho un problema con il rowspan e non riesco a trovare la soluzione.
il codice sotto, funziona ma non come vorrei io

<table cellspacing="0" border="0">
<tr>
 <td background="Other/LeftTop.png" width="34" height="12"></td>
 <td background="Other/Top.png" width="1" height="12"></td>
 <td background="Other/RightTop.png" width="14" height="12"></td>
 <td rowspan="2"></td> <td rowspan="2"></td>
</tr>
<tr>
 <td background="Other/Left.png" width="34" height="1"></td>
 <td>prova proviamoci provetta provina</td>
 <td background="Other/Right.png" width="14" height="1"></td>
 <td></td>
 <td></td> 
</tr>
<tr>
 <td background="Other/Left_2.png" width="34" height="24"></td>
 <td></td>
 <td background="Other/Right_2.png" width="14" height="24"></td>
 <td rowspan="2" background="Other/Time.png" width="1" height="36">19.30</td>
 <td rowspan="2" background="Other/TimeRight.png" width="8" height="24"></td>
</tr> 
<tr>
 <td background="Other/LeftBottom_2.png" width="34" height="12"></td>
 <td background="Other/Bottom.png" width="1" height="12"></td>
 <td background="Other/RightBottom_2.png" width="14" height="12"></td>
 <td></td>
 <td></td> 
</tr> 
</table>

Se nella seconda riga (della tabella) aggiungo il rowspan="2" si spostano le celle

<table cellspacing="0" border="0"> 
<tr>
 <td background="Other/LeftTop.png" width="34" height="12"></td>
 <td background="Other/Top.png" width="1" height="12"></td>
 <td background="Other/RightTop.png" width="14" height="12"></td>
 <td rowspan="2"></td> <td rowspan="2"></td> 
</tr> 
<tr>
 <td background="Other/Left.png" width="34" height="1"></td>
 <td rowspan="2">prova proviamoci provetta provina</td>
 <td background="Other/Right.png" width="14" height="1"></td>
 <td></td>
 <td></td> 
</tr> 
<tr>
 <td background="Other/Left_2.png" width="34" height="24"></td>
 <td></td>
 <td background="Other/Right_2.png" width="14" height="24"></td>
 <td rowspan="2" background="Other/Time.png" width="1" height="36">19.30</td>
 <td rowspan="2" background="Other/TimeRight.png" width="8" height="24"></td> 
</tr> 
<tr>
 <td background="Other/LeftBottom_2.png" width="34" height="12"></td>
 <td background="Other/Bottom.png" width="1" height="12"></td>
 <td background="Other/RightBottom_2.png" width="14" height="12"></td>
 <td></td>
 <td></td> 
</tr> 
</table>

Perché si sposta tutto??? e cosa posso fare per risolvere tutto??
Grazie