system works too slowly

the system works slowly, in spite of it's xubuntu. for example, internet browser load about 2-3 minutes, and video dvd just stop picture on the first frame, while play cursor is moving, heroes voices are played, and if audio cd played, and another application started, it becomes paused 1-2 second, then continued, then paused, until another app is full loaded.

This pc works on Windows XP, and debian etch and works without such a problem.

It seems to me that some driver not in kernel, so it use unappropriate driver or generic?.
m@ubuntu:~$ lsb_release -rd
Description: Ubuntu 12.04.1 LTS
Release: 12.04
lm@ubuntu:~$

m@ubuntu:~$ apt-cache policy pkgname
N: Unable to locate package pkgname
lm@ubuntu:~$ sudo apt-cache policy pkgname
[sudo] password for lm:
N: Unable to locate package pkgname
lm@ubuntu:~$

REsume :
all applications works toooo slowly.
i use vlc and expect to see movie
instead it start plying and remain on the first frame while audio stream is running.