Vista - Powershell Newbie

Hi,

I'm now to this forum, hi to everyone. I normally use command prompt and have now decided to use powershell. I have the following script:-

Set-Location "C:\Documents and Settings\Admin\Desktop\TEST"
$yesterday=(get-date (get-date).AddDays(-1) -uformat %Y%m%d)
rename-item 20090408_04.LOG "$yesterday.a04"

Fisrtly, I cannot get the script to run, I've set the file *.ps1 to open with powershell, I get a flash of red writing and it disappears too quickly. Therefore I have no idea what the error is.

The Execution Policy is set to unrestricted.

Secondly, the files I'm trying to rename change on a daily basis (today's date)_04.LOG, (today's date)_05.LOG, (today's date)_06.LOG etc to $yesterday.a04, $yesterday.a05, $yesterday.a06 etc. How would I do this???

I know, this is my first time, I'm asking loads of questions....

Thanks in advance.