i am also not able to run universe sandbox on steam or the free version. i have done all the suggested troubleshooting regarding .net verification and re installation. verification of files show no missing files, the drive has been fully de-fragmented and checked for errors.
Running XP PRO SP3
Time of this report: 7/10/2011, 17:10:11
Machine name: OMEGA
Operating System: Windows XP Professional (5.1, Build 2600) Service Pack 3 (2600.xpsp_sp3_gdr.100216-1514)
Language: English (Regional Setting: English)
System Manufacturer: ECS
System Model: A880LM-M
BIOS: Default System BIOS
Processor: AMD Phenom(tm) II X6 1090T Processor, MMX, 3DNow (6 CPUs), ~3.2GHz
Memory: 3328MB RAM
Page File: 909MB used, 8259MB available
Windows Dir: C:\WINDOWS
DirectX Version: DirectX 10.0 (4.10.0000.5512)
DX Setup Parameters: Not found
DxDiag Version: 5.03.2600.5512 32bit Unicode