Finally, here’s an official note on Windows 7 RC release “I’m pleased to share that the RC is on track for April 30th for  download by MSDN and TechNet subscribers. Broader, public availability will begin on May 5th. Many of your suggestions helped us refine the new and improved taskbar, the behavior of Aero Peek, Touch, Windows Media Player, and much more,”
announced Brandon LeBlanc.

In a releated news, many sites posted the leaked screenshots of upcoming release candidate Build 7100:

Here are some of the details:

Build String: 7100.0.winmain_win7rc.090421-1700
File Name: 7100.0.090421-1700_x86fre_client_en-us_Retail_Ultimate-GRC1CULFRER_EN_DVD.iso
Size: 2.36GB // 3.04 GB
MD5 Hash: 8867C13330F56A93944BCD46DCD73590 (x86 only)
CRC32: E8A1C394
SHA-1: 7D1F486CA569EFFFFB719CFB48355BB7BF499712
Torrent Hash: C738F422D 6C36C36A 655BEFB3 21E51E4A 2C84B7EE // A4835C20 4C7FC504 704C9376 73A8762A B9F2E761

Furthermore to check if your file has been tampered with, you can easily compare the file hash of your x86 (32-bit) ISO file with HashTab against the following.

CRC32: E8A1C394
MD5: 8867C13330F56A93944BCD46DCD73590
SHA-1: 7D1F486CA569EFFFFB719CFB48355BB7BF499712