My laptop came with Vista but I don't like Vista so I nuked it and installed XP. It took me a while to find all the XP hardware drivers I needed but I have suceeded at last.
If you want to downgrade from Vista here are the drivers you need to run XP on your 5601Z.
The Ethernet driver for my Acer Aspire 5610Z was the last one I found you can get it here:
Most of the other drivers for XP are here ftp://ftp.work.acer-euro.com/notebook/aspire_5610/driver/
My computer has the Broadcom wireless adaptor and it can be found here
Some models have the atheros card and it's drivers are here ftp://ftp.work.acer-euro.com/notebook/aspire_5610/driver/Wireless%20Lan%20Driver%20802bg%20Atheros%20Ver.22.214.171.124.zip
Both of the links for the wireless driver came from :
How does my machine run with XP? Super fast! No more waiting forever just to boot the OS! Sure it took all day to round up the drivers but it was worth it.