Your computer specifications
https://www.cnet.com/products/dell-xps-400-pentium-d-820-2-8-ghz-1-gb-160-gb-lcd-19/specs/
Your motherboard chipset specs and mobo review
http://www.pcstats.com/articleview.cfm?articleid=2068&page=2
Your mobo/chipset CPU support Intel Core 2 Extreme
X6800 - HH80557PH0774M / BX80557X6800 / X6800, 2.93 GHz, FSB 1066 MHz, L2 4 MB
http://www.cpu-upgrade.com/mb-Intel_(chipsets)/945P_Express.html
Top Core2 Duo model supported (Intel Core2 Extreme X6800 @ 2.93GHz) Performance: Passmark CPU Mark = 1885
https://cpubenchmark.net/cpu.php?cpu=Intel+Core2+Extreme+X6800+%40+2.93GHz&id=933
Your Pentium D 945 Performance not listed but falls between the 940 and 950
Intel Pentium D 940 @ 3.20GHz Passmark CPU Mark = 710
Intel Pentium D 950 @ 3.40GHz Passmark CPU Mark = 740
CSGO (Counter-Strike: Global Offensive) Minimum System Requirements (Intel Core 2 Duo E6600)
https://www.systemrequirementslab.com/cyri/requirements/counter-strike-global-offensive/11422
CPU: Intel Core 2 Duo E6600 processor or better
RAM: 2 GB
OS: Windows 7/Vista/XP
Video Card: Video card must be 256 MB or more and should be a DirectX 9-compatible with support for Pixel Shader 3.0
Intel Core2 Duo E6600 @ 2.40GHz Performance: Passmark CPU Mark = 1554
http://www.cpubenchmark.net/cpu.php?cpu=Intel+Core2+Duo+E6600+%40+2.40GHz