Minimum system requirements for Microsoft Security Essentials
Operating System: Windows XP Service Pack 3 (SP3)*; Windows Vista (Service Pack 1, or Service Pack 2)*; Windows 7*
For Windows XP, a PC with a CPU clock speed of 500 MHz or higher, and 256 MB RAM or higher.
For Windows Vista and Windows 7, a PC with a CPU clock speed of 1.0 GHz or higher, and 1 GB RAM or higher.
VGA display of 800 × 600 or higher.
200 MB of available hard disk space.
An Internet connection is required for installation and to download the latest virus and spyware definitions for Microsoft Security Essentials.
Internet Browser:
Windows Internet Explorer 6.0 or later.
Mozilla Firefox 2.0 or later.
Microsoft Security Essentials also supports Windows XP Mode in Windows 7. For more information see the system requirements for Windows XP Mode in Windows 7.
So to answer your question, yes it works on XP.
My Computer
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Home Built desktop, Dell G15 5511 Gaming laptop,MS Surface Pro 7 tablet
OS
W10 Pro desktop, W11 laptop, W11 Pro tablet (all 64-bit)
CPU
3.7Ghz 8700K i7, i7-11800H, i7-1065G7
Motherboard
ASUS TUF Z370-Pro Gaming in desktop
Memory
16G desktop, 16G laptop, 4G tablet
Graphics Card(s)
AMD Radeon RX580, RTX 3060, Intel Iris Plus
Sound Card
High Definition Audio (Built-in to mobo)
Monitor(s) Displays
Samsung U32J59 32" (2x), 15.6", 12"
Screen Resolution
3840x2160, 3840x2160, 1920x1080, 2160x1440
Hard Drives
500G SSD for OS; 2T, 10T & 15T HDDs for Data on Desktop, 1TB SSD laptop, 128G SSD tablet.
PSU
Corsair CX 750M
Case
Antec 100
Cooling
CM 212+
Keyboard
IBM Model M - used continuously since 1986
Mouse
Microsoft Pro IntelliMouse
Internet Speed
400M down 8M up
Antivirus
Windows Defender
Browser
FireFox
Other Info
Built my first computer (8Mhz 8088cpu, 640K RAM, 20MB HDD, 2 360K floppy drives) in 1985 and have been building them for myself, relatives and friends ever since.