Vistalizator is a free and simple to use utlity which lets you change the display language in windows 7, however this utlity also works for vista also. You can add various other different languages through the language packs you have downloaded.

This simple application could really save a hell lot of time, while changing the display language in windows 7, however the if you do it windows 7 interface it may take more time, here with this application you can add languages just by locating the language packs you have downloaded. 

Here are the links to download language packs for 32 bit and 64 bit windows 7, let me know if I missed some language pack in the list below 

Download 32-bit Windows 7 RC Language Packs

English (EN-US): en-us-x86.zip
German (DE-DE): de-de-x86.zip
Spanish (ES-ES): es-es-x86.zip
French (FR-FR): fr-fr-x86.zip
Italian (IT-IT): it-it-x86.zip
Japanese (JA-JP): ja-jp-x86.zip
Simplified Chinese (ZH-CN): zh-cn-x86.zip
Hong Kong Chinese (ZH-HK): zh-hk-x86.zip
Traditional Chinese (ZH-TW): zh-tw-x86.zip
Korean (KO-KR): ko-kr-x86.zip
Bulgarian (BG-BG): bg-bg-x86.zip
Czech (CS-CZ): cs-cz-x86.zip
Danish (DA-DK): da-dk-x86.zip
Greek (EL-GR): el-gr-x86.zip
Estonian (ET-EE): et-ee-x86.zip
Finnish (FI-FI): fi-fi-x86.zip
Hungarian (HU-HU): hu-hu-x86.zip
Lithuanian (LT-LT): lt-lt-x86.zip
Latvian (LV-LV): lv-lv-x86.zip
Norwegian (NB-NO): nb-no-x86.zip
Dutch (NL-NL): nl-nl-x86.zip
Polish (PL-PL): pl-pl-x86.zip
Portuguese (PT-PT): pt-pt-x86.zip
Brazilian Portuguese (PT-BR): pt-br-x86.zip
Romanian (RO-RO): ro-ro-x86.zip
Slovak (SK-SK): sk-sk-x86.zip
Slovenian (SL-SI): sl-si-x86.zip
Swedish (SV-SE): sv-se-x86.zip
Arabic (AR-SA): ar-sa-x86.zip
Hebrew (HE-IL): he-il-x86.zip
Croatian (HR-HR): hr-hr-x86.zip
Serbian or Latin (SR-LATN-CS): sr-latn-cs-x86.zip
Thai (TH-TH): th-th-x86.zip
Turkish (TR-TR): tr-tr-x86.zip
Ukrainian (UK-UA): uk-ua-x86.zip
Russian (RU-RU): ru-ru-x86.zip

Download 64-bit Windows 7 RC Language Packs

English (EN-US): en-us-x64.zip
German (DE-DE): de-de-x64.zip
Spanish (ES-ES): es-es-x64.zip
French (FR-FR): fr-fr-x64.zip
Italian (IT-IT): it-it-x64.zip
Japanese (JA-JP): ja-jp-x64.zip
Simplified Chinese (ZH-CN): zh-cn-x64.zip
Hong Kong Chinese (ZH-HK): zh-hk-x64.zip
Traditional Chinese (ZH-TW): zh-tw-x64.zip
Korean (KO-KR): ko-kr-x64.zip
Bulgarian (BG-BG): bg-bg-x64.zip
Czech (CS-CZ): cs-cz-x64.zip
Danish (DA-DK): da-dk-x64.zip
Greek (EL-GR): el-gr-x64.zip
Estonian (ET-EE): et-ee-x64.zip
Finnish (FI-FI): fi-fi-x64.zip
Hungarian (HU-HU): hu-hu-x64.zip
Lithuanian (LT-LT): lt-lt-x64.zip
Latvian (LV-LV): lv-lv-x64.zip
Norwegian (NB-NO): nb-no-x64.zip
Dutch (NL-NL): nl-nl-x64.zip
Polish (PL-PL): pl-pl-x64.zip
Portuguese (PT-PT): pt-pt-x64.zip
Brazilian Portuguese (PT-BR): pt-br-x64.zip
Romanian (RO-RO): ro-ro-x64.zip
Slovak (SK-SK): sk-sk-x64.zip
Slovenian (SL-SI): sl-si-x64.zip
Swedish (SV-SE): sv-se-x64.zip
Arabic (AR-SA): ar-sa-x64.zip
Hebrew (HE-IL): he-il-x64.zip
Croatian (HR-HR): hr-hr-x64.zip
Serbian or Latin (SR-LATN-CS): sr-latn-cs-x64.zip
Thai (TH-TH): th-th-x64.zip
Turkish (TR-TR): tr-tr-x64.zip
Ukrainian (UK-UA): uk-ua-x64.zip
Russian (RU-RU): ru-ru-x64.zip