Just went through three days of run around with Parallels support trying to figure out why I couldn't access a Mac folder through a Mac alias under WinXP using Parallels Shared Folders. For example, if you have a Mac folder called "Target" to which you've made a Mac alias called "Target Alias" and attempt to access "Target" by double clicking on "Target Alias" in WinXP through Parallels Shared Folders, you'll get a Windows dialog box telling you that XP doesn't recognize the file type of the alias. Parallels support told me to de-install and re-install Parallels Tools multiple times on multiple machines, reboot, run Disk Utility and repair permissions, etc., all to no avail. Finally the problem was escalated and I'm told today that Mac aliases aren't supported under Parallels Shared Folders, at least as of build 3188. Hopefully this information will get added to a FAQ somewhere, but until then here it is...
It's an easy solution. Instead of creating an alias, create a symbolic link. Open the terminal and type something like this: ln -s /Library/ ~/System-Library Windows can access that just fine. I have been doing that since the first beta of parallels with windows shares.
I also would like support for Mac aliases introduced, to 'translate' (correct term?) them from aliases to Windows shortcuts. Personally, I want to learn more about Unix and the Terminal, but I don't think every user would want to or should need to.