You have multiple problems going here.
AMD Sempron(tm) Processor 2800+ 1.81 GHz
RAM: 1 GB
SO Windows 7 Ultimate 32bits
ATI Radeon 9550/X1050 Series 256MB
-Your RAM just scrapes on the minimum but it should be at least 2GB+ in order to have flowing gameplay: Minimum: 1GB (1024 MB)
-Your Processor CPU is quite low at 1.81GHz but still would be fine for usage.
-Your Graphics Card is 256MB, which is VERY LOW: GeForce FX 5700 or Radeon 7600 w/512mb memory is the minimum to play, that is your problem. Your Video (Graphics Card) is too low and needs to be replaced with a newer version of 512mb +
You can view all this information here; http://wolfteam.aeriagames.com/overview/sysreq
ALSO NOTE: You NEED to get an Anti-Virus. You NEED to have your Firewall ON. You NEED to have Windows Defender (If you don't have an Anti-Virus).