Here's some tips if you do decide to upgrade. If your hardware and
software are supported and you don't connect to a corporate domain
then Vista works great. I prefer it over XP. If you connect to a
corporate domain talk to the IT department before upgrading to
make sure they support Vista.
1) Backup your PC.
2) Back it up again.
3) Test your backups.
If you skip the above steps please don't whine that the upgrade
trashed all your files. Any process that involves this many
changes to the file system is fraught with danger. If you don't
have a full backup of your pc before starting the upgrade you are
an idiot and shouldn't really have a pc to start with

This may
sound harsh but it is reality.
4) Run the latest version of the Upgrade Advisor and note anything
it flags. 5) Uninstall (not disable) all antivirus, antispyware,
firewall, disk utility, and system utility programs even if the
upgrade advisor doesn't mention them. You will need to install
Vista compatible versions after the upgrade is finished.
6) Uninstall (not disable) all programs that the upgrade advisor
flags as possible problems. You will need to install Vista
compatible versions after the upgrade is finished.
7) If possible remove all hardware that the upgrade advisor flags
as incompatible.
8) Make sure you have Vista compatible drivers and software for
all your hardware devices burned to CD. Don't just look for
drivers that the upgrade advisor mentioned. If possible have
drivers ready for everything. 9) Physically unplug any external
devices like portable hard drives, printers, card readers, flash
drives, cameras, etc.. 10) Run a chkdsk on all the partitions on
all hard drives still connected. 11) Defrag the system and boot
partitions. 12) Start the Vista upgrade process.