Sorry, I was a bit busy.
A few more questions (I know, It's annoying
)
what pc model do you have? (exact model)
If you take it out (your new ram stick) does windows loads normally or is the activition screen ok?
What kind of ram your new one is?
And how much mb/gb is the old one?
(I need this info to check if it's of and if your system supports it)
Ok, first thing, if U can , try go to safe mode(f8 at startup) and try activate from there
Start>run and type oobe/msoobe /a
and click ok
I also found some problems being related to Internet explorer (yeah, I know weird...)
try uninstalling/reinstalling or updating it. Then try the activition again.
Here are some links that might help:
http://www.mydigitallife.info/fix-windows-xp-activate-windows-now-wizard-not-show-nor-display-error/
http://answers.microsoft.com/en-us/windows/forum/windows_xp-windows_install/windows-xp-activation-window-does-not-start-open/84716389-40fd-4d29-9005-a262d47a0a1d
http://support.microsoft.com/kb/314935
If you don't have any luck with safe mode or IE, just answer my questions back , and we'll see.