Of course there are poker apps.... there are a bunch of them, most you have to pay for.
Realdice texas hold em is free on microsoft's total access though:
http://www.microsoft.com/windowsmobi...xasholdem.mspx
You have to sign up for a windows live account to get the download, but it is free.
You can play alone or online, which is what sets this poker game apart from the others.
If you want more options and willing to pay try:
http://store.handmark.com/products/detail.php?id=572&&&
http://www.astraware.com/all/casino/?link=1/top/4
http://www.concretesoftware.com/wind...hellmuth.shtml
http://www.concretesoftware.com/wind...oldem_nl.shtml