Need to upgrade my Athlon processor - help please!

[debswd23]

I am wanting to install the new Tomb raider game and it keeps saying 'SSE instruction set not supported'. So I'm told I need to have an Athlon XP 2000+ processor to run it. My comp spec. is as follows -
------------------
System Information
------------------
Operating System: Windows XP Home Edition (5.1, Build 2600) Service Pack 2 (2600.xpsp_sp2_gdr.070227-2254)
Language: English (Regional Setting: English)
System Manufacturer: Tiny Computers
System Model: MS-6378
BIOS: Ver 1.64
Processor: AMD Athlon(tm) processor, MMX, 3DNow, ~1.3GHz
Memory: 376MB RAM
Page File: 336MB used, 2259MB available
Windows Dir: C:\WINDOWS
DirectX Version: DirectX 9.0c (4.09.0000.0904)
DX Setup Parameters: Not found
DxDiag Version: 5.03.2600.2180 32bit Unicode

The motherboard had this on it - MS-6378 VER 3

Please could someone let me know if this processor would be suitable for my computer. Also is it a Socket A processor required and would the fan I have now still be ok to use? Finally if I buy it second hand will I need to buy silver paste aswell? Thankyou for your time.

[gshv]