i honestly dont believe theres any chance of party installing something like this
im not sure if you know how the whole spyware industry works
ill assume you dont
basically, there are many types of spyware. The biggest type is the one which monitors the pages you are browsing - it doesnt actually remember the info and then send it to anyone but it takes a snapshot of the page quickly, scans it for keywords and then scours its database for a suitable advertiser that the spy company has partnered with. At this point a related ad will pop up.
Now not all act in this way - some pop up every time you open up, some at a random time or event.
One of the main section of people to add spyware to your computer is developers who add spyware to their free version. For example, i downloaded an FTP last year. If you paid for it there were no ads but if you didnt the download came with spyware on it to fund the developer - that particular site was honest about it and warned downloaders about it and said that it was to cover the cost of him working full time on the script. Fair enough.
However, as you know not all sites are this fair and some hide it on their downloads.
Anyways - im moving away from my main point here. The main point is that although money can be made, it isnt actually that much. Most sites which add it are not making that much money or are adding spyware to fund their work (ie. like scripts found on downloads.com)
Now i aint disputing that some sites might put in certain things on your pc that they arent 100% honest about but i refuse to believe that any of the major sites would add spyware to their downloads
Using your example of party poker, they have on average 60,000 players at the table at any given time. Do you have any idea how much rake this site is collecting? Put simply party is probably worth close to a billion dollars. They would be complete idiots to add spyware to their downloads to make a few extra cents (and honestly per download thats probably all spyware companies make per ad)
do this for me
* completely uninstall party poker from your computer
* install spysweeper, spydoctor, ad aware etc -make sure you have a few running
* Download party again and install
post any messages that appear when installing party
if nothing appears then party is clean, if it isnt then we would be able to track down exactly what it is (you have to remember that when installing anything with spysweeper, 90% of the time it pops up asking if you want the file added to your safe list - this is because your registry is being edited, which is required by most applications....for example, adding something to start up or whatever ) | 
cos it could have been a number of things
