Some possibilities:
1. The sound card/drivers are not DirectX 8.1 compatible. Try updating the drivers.
2. The video card is an S3 Pro Savage (I don't know about SiS). These cards do not properly support DirectX 8 and above. The only solution is to replace it (and you can get Radeon 7000 for $20)
3. Some other program such as spyware or a virus could be affecting it. Try running a scan.
4. The computer doesn't meet the system requirements. What are the system specs?
5. The operating system may be unstable in some way preventing it from performing properly.

Further details such as system specifications would be nice.

"You level up the fastest and easiest if you do things at your own level and no higher or lower" - useful tip My 2D game - release on Jun 13th; My tutorials