Indeed good to know, thank you! But is there a place to manually download definition updates that works in XP?
The last known Definition Update that works with XP/Vista MSE is 1.291.2489.0, if you go newer than that, it will fail to install the definitions and there's no known "trick" that enables installation of latest updates.
;Microsoft Security Essentials 4.10.209.0 ( the 32 bit version is the last working xp-32bit version ) ;32bit: XP, Vista, win7 ;64bit: Vista, win7 Code: 6e7ec8aad8322253980c7037f01d1d4bfef95570 *[en-us] mseinstall_32bit.exe 98b98f456bc2f8c95dacf45360885fa949e7ee71 *[en-us] mseinstall_64bit.exe 3fbbf7975863921346f526d848d6ab0be5b77d45 *[bg-bg] mseinstall_32bit.exe ee3e03b66e79251c877a1374f542fa4ecc7752bc *[bg-bg] mseinstall_64bit.exe 81750509c56e5be797dede162273095be17bd5ca *[cs-cz] mseinstall_32bit.exe 24623b1ce2a7a736916697fa21eb636a9b1b76f4 *[cs-cz] mseinstall_64bit.exe 23e0f90e18a92ec92dcfc4d7378cd361c9c165d5 *[da-dk] mseinstall_32bit.exe e7782c184598cabdc03d0415375ef0293fd91e8c *[da-dk] mseinstall_64bit.exe aaa86178d5a8c19e2f3a85ae479d9d200c2c3908 *[de-de] mseinstall_32bit.exe 3eea05e9b8ec0df77a10013eae45880a573ac0cf *[de-de] mseinstall_64bit.exe ae89e2f2e349a413ef4e73b044c155eb1ed80b60 *[el-gr] mseinstall_32bit.exe e5142acff2d2e04fa783142c8ab31502a8dc24f9 *[el-gr] mseinstall_64bit.exe 5e6965ddedbaf15a71dee4a2c30f83770bd9834a *[es-es] mseinstall_32bit.exe f3130b16d023597d34dea47c3e5db6dfb5b17250 *[es-es] mseinstall_64bit.exe 561156e883d27d6e40be93382ce672523fcd363a *[et-ee] mseinstall_32bit.exe c4b4281423b5fa9ea378fe68fdae07a928084afe *[et-ee] mseinstall_64bit.exe fef6585738842d204afa5aa92be55b8dc9c1d3fc *[fi-fi] mseinstall_32bit.exe 9f1b36d7fdfb095a4d03136d393ebcebfc41aaa6 *[fi-fi] mseinstall_64bit.exe e2851dbd248980569e46ce1e8f21d2acff759adf *[fr-fr] mseinstall_32bit.exe c8b84ea54a8ebc8cac7090656acf7cbcb1b9e3f6 *[fr-fr] mseinstall_64bit.exe 8ee0a6e3d20e8b1064f03418c5888322f39b2279 *[hr-hr] mseinstall_32bit.exe b690d02d6dd1ff4a795a4b3eaa00d05c84755394 *[hr-hr] mseinstall_64bit.exe 1bb2b581129d077054125cbf3d8094470717596b *[hu-hu] mseinstall_32bit.exe ad01745bb6253f3b09390af59d9fdd593db43dfe *[hu-hu] mseinstall_64bit.exe 9dda7f2c53d22dcb8458e4086c71319ce7fb39c2 *[it-it] mseinstall_32bit.exe 5ae83f2a91dc105524112332ce072c33cc1ff2d0 *[it-it] mseinstall_64bit.exe f3b5e08e0392e2dd2fb28c3e536e48e3d3e2f571 *[ja-jp] mseinstall_32bit.exe 857f34fab2e5345460e5f2122bef8aad2a3aa3ee *[ja-jp] mseinstall_64bit.exe 12eef21c0557e66a9cde4765cee754e1e4a8dab7 *[ko-kr] mseinstall_32bit.exe 9e2d162abaafc7500846e5a96cd96bb31502867d *[ko-kr] mseinstall_64bit.exe 70e73b780d99e4a30ccc560421d3bb4fbcc6493b *[lt-lt] mseinstall_32bit.exe 7688a8a6d0f48ec1b6edf2d33f50ac650f487b65 *[lt-lt] mseinstall_64bit.exe 3847f728b0477352543df04d6d75596e2019bda3 *[lv-lv] mseinstall_32bit.exe 3648c8261332f779f9bf06707b1585c1bb97aeb6 *[lv-lv] mseinstall_64bit.exe 90a5778859ce171ce0ccbf50f63d626eea298ae5 *[nb-no] mseinstall_32bit.exe d8a95d97717b7469f42323ce36a0d56ea6480e94 *[nb-no] mseinstall_64bit.exe 8b84c51bc293e815cdb55ae19f67f4aa2efc9038 *[nl-nl] mseinstall_32bit.exe 501ee70aaf1504c3014cf8f90fabf2557a29cc43 *[nl-nl] mseinstall_64bit.exe 6bec142e3ed4e2138e20de5d4fa27c82c73afc48 *[pl-pl] mseinstall_32bit.exe 011c6bd9bc45447d9543e1a91cc46f20cc97004e *[pl-pl] mseinstall_64bit.exe 30b9263ef94145924c257bd40921d44d92790a34 *[pt-br] mseinstall_32bit.exe 84da2b9b0644b169c20a39d69cb7014a5cb18d3f *[pt-br] mseinstall_64bit.exe 0ac4bcfa024fb43478e489f0d4a9cd9ac70fbd57 *[pt-pt] mseinstall_32bit.exe a7a6dc0a1237a20c94a8f348c3a139d7ebee974f *[pt-pt] mseinstall_64bit.exe 63d5e934e2440e1d8b11c77710ea33e006928112 *[ro-ro] mseinstall_32bit.exe 52b42df7bae53d661044867b83ac23da3f08b455 *[ro-ro] mseinstall_64bit.exe 102970309ad9e0c151b8524e51a365ab170b77fd *[ru-ru] mseinstall_32bit.exe 3194a2f2d9e9f1a7ffff3545883ee7624667714f *[ru-ru] mseinstall_64bit.exe a9a43084d6abd3166c8ffb043a97bfbfc1cc60c0 *[sk-sk] mseinstall_32bit.exe 391920db7a84ca4b4153b351f88e99d40a680ebc *[sk-sk] mseinstall_64bit.exe 361d5f815949ec8a05b2a74e0492645ad45337da *[sr-la] mseinstall_32bit.exe 9c0b64b9cf87eb2dc32291009f881aabc7384b1b *[sr-la] mseinstall_64bit.exe 08465c2833d6b7789092681ec887156237568964 *[sv-se] mseinstall_32bit.exe ac70ad4c263c0a5adf2cae86dcd2433582c53eea *[sv-se] mseinstall_64bit.exe 091cc5a1a74996af7aace7fd4b0d7a1e02a4390f *[th-th] mseinstall_32bit.exe c6f3e4bc62e5c63421e0051dfdd25833e8436466 *[th-th] mseinstall_64bit.exe c70ef22c6a0ade11aeaf84a874a24e5953ec8d8f *[tr-tr] mseinstall_32bit.exe 3586731803a1811365b23333aa39ce40759e19f1 *[tr-tr] mseinstall_64bit.exe 5cccc375cabcc98bde58f49580b04f8a93a328b5 *[uk-ua] mseinstall_32bit.exe 95f4dd145698618ee18f63e232c8bdbaa2163dff *[uk-ua] mseinstall_64bit.exe f8c0bd32360ca3784734d3c860d09ab5adcda971 *[vi-vn] mseinstall_32bit.exe fa06e65f179e5bc78af0ed8d039f1cf4cf504c6e *[vi-vn] mseinstall_64bit.exe afaf77b3fea8d59aa4e2a5750e3c670b7f87a606 *[zh-cn] mseinstall_32bit.exe 0c2b6705b336de4ff2c4f74105f9f4e38f9c6840 *[zh-cn] mseinstall_64bit.exe 81302c098aad90fcf907e7ee4aff02509d93361a *[zh-tw] mseinstall_32bit.exe a0adc2d195186aa74a2c4218cb9f1076d86b9443 *[zh-tw] mseinstall_64bit.exe the install (Setup) files are still online and the virus definition files still update automatic idk why some Member say 209 was not working on XP (maybe they use XP-64bit version)
Ricktendo64 made a Microsoft Security Essentials 4.6.305.0 custom installer for XP. that version was Released in Sep 2014. So, I dont know the EOL of this version but i think is possible get newer definitions that official XP version