Vista Lagging Horribly

my brother recently bought an upgrade copy of windows vista home premium.
he successfully installed it, but when it boots up, there is a 6 second lag in everything. this includes opening the start menu, the highlights on start menu items when you hover the mouse over it, clicking to open programs, typing things in, and the mouse lags every once in a while.

when we installed it, we chose the custom install, because the upgrade was disabled for some reason, and had the old copy of XP moved to a folder on the harddrive called windows old.
also, I don't know if this will help or not, but for some reason during installation, when he put the CD key in, it didn't accept it.

heres the system specs in case you need them:

AMD Athlon 64x2 Dual-core
ATI Radeon X1300
2GB Ram
80GB Harddrive

 

Upgrading over a previous OS has always been an issue, I remember when I first installed XP over Win98se how slow the system was until I formated out and reinstalled. For XP all you had to do to install an upgrade to a fresh hard drive was to put your 98 cd in the rom drive and enter your serial number. I remember reading that Vista was similar. The article talked about pre installing vista as a trial to a blank drive but not registering it, and then install the full version over that like an update and registering to be able to install an upgade version as a full install.

See here:

Code:

http://gizmodo.com/gadgets/pcs/how-to-install-a-vista-upgrade-on-a-blank-hard-drive-232770.php

 

well, we found out how to fix it. apparently, he had to upgrade his computer from windows xp home to vista in order for it to actually upgrade and not lag.