this is a sample wpl file
Code:
<?wpl version="1.0"?>
<smil>
    <head>
        <meta name="Generator" content="Microsoft Windows Media Player -- 9.0.0.3349"/>
        <author/>
        <title>Sample</title>
    </head>
    <body>
        <seq>
            <media src="F:\Muziek\A\Arctic Monkeys - A Certain Romance.mp3" tid="{A8E9964A-12E2-4812-A0EE-DBFC53345C55}"/>
            <media src="F:\Muziek\A\Arctic Monkeys - Dancing Shoes.mp3" tid="{F5382CF2-DEC2-4753-B63B-804EE48E5BAD}"/>
            <media src="F:\Muziek\A\Arctic Monkeys - Fake Tales Of San Fransisco.mp3" tid="{0A6FA79A-7D7F-4D0C-AD4D-1FC391FD12D5}"/>
            <media src="F:\Muziek\A\Arctic Monkeys - From The Ritz To The Rubble.mp3" tid="{2F448BE4-3B8D-4A37-8C3B-9C6654FB9778}"/>
            <media src="F:\Muziek\A\Arctic Monkeys - I Bet You Look Good On The Dancefloor.mp3" tid="{E6337358-9EA1-4449-ABFD-AB67B17C5622}"/>
            <media src="F:\Muziek\A\Arctic Monkeys - Mardy Bum.mp3" tid="{49D858D9-64F0-4177-A6E1-D5D654CB40E5}"/>
            <media src="F:\Muziek\A\Arctic Monkeys - Perhaps Vampires Is a Bit Strong But....mp3" tid="{2EE4020F-037F-43AA-826B-2992806ACD83}"/>
            <media src="F:\Muziek\A\Arctic Monkeys - Red Light Indicates Doors Are Secured.mp3" tid="{8F3AFBC2-679C-4D88-954B-DE37C3004324}"/>
            <media src="F:\Muziek\A\Arctic Monkeys - Riot Van.mp3" tid="{3FC27498-2ABE-4C8C-90BC-6DC2564F5A65}"/>
            <media src="F:\Muziek\A\Arctic Monkeys - Still Take You Home.mp3" tid="{30287325-3401-4A27-B8C0-7993F027E0F1}"/>
            <media src="F:\Muziek\A\Arctic Monkeys - The View From The Afternoon.mp3" tid="{E29FA33E-9884-4145-AC29-DECD8A65A818}"/>
            <media src="F:\Muziek\A\Arctic Monkeys - When The Sun Goes Down.mp3" tid="{7D942F6F-1F54-4077-9278-4181AB082B99}"/>
            <media src="F:\Muziek\A\Arctic Monkeys - You Probably Couldn&apos;t See For The Lights But You Were Staring Straight At Me.mp3" tid="{5754590A-9BAF-4055-861B-29862735ACF4}"/>
        </seq>
    </body>
</smil>
I understand most of this, but what's the 'tid'?

(btw: what is a better forum section for this question?)