Recently Microsoft announced that they are ready with Windows 7 RTM (Release to Manufacture) and the original image files are already out for download at many websites. But it is advisable to crosscheck the filehashes to avoid getting infected with rootkits and other malware. A German Microsoft employee had published the Windows 7 checksums. This will come handy when you want to check CRC32/SHA1 hashes.

• Windows 7 Retail Ultimate E english (x86)
  Name: 7600.16385.090713-1255_x86fre_cliente_en-us_Retail_UltimateE-GRMCEULFRER_EN_DVD.iso
  CRC: 0x953EFBCC
  SHA-1: 0xBC10F09B86DCBAF35B31B0E6FBA7D006ACAAD28D
• Windows 7 Retail Ultimate E english (x64)
  Name: 7600.16385.090713-1255_x64fre_cliente_en-us_Retail_UltimateE-GRMCEULXFRER_EN_DVD.iso
  CRC: 0x77BE890E
  SHA-1: 0x029DCCEDD7691206010F84CE58343405A4DA92C9
• Windows 7 Retail Ultimate english (x86)
  Name: 7600.16385.090713-1255_x86fre_client_en-us_Retail_Ultimate-GRMCULFRER_EN_DVD.iso
  CRC: 0xC1C20F76
  SHA-1: 0x5395DC4B38F7BDB1E005FF414DEEDFDB16DBF610
• Windows 7 Retail Ultimate english (x64)
  Name: 7600.16385.090713-1255_x64fre_client_en-us_Retail_Ultimate-GRMCULXFRER_EN_DVD.iso
  CRC: 0x1F1257CA
  SHA-1: 0x326327CC2FF9F05379F5058C41BE6BC5E004BAA7

Guide: How to verify MD5/SHA1 checksums