WinRar

1.WinRAR, like other software, has recorded the date that you first installed it (I don't know where it store, it may be as a registry file or some log file in some "hidden" folder).
Even if you uninstall it and then install it again, the file is still there and it will check if 40 days has passed since the date it has recorded. Therefore, it is no use installing it again.

2. I remember there is a software which can create "LAYER" in the hard disk. Once you install a "TRIAL" software, you create a new "LAYER" and install on that. Then, when the trial period has expired, you can just delete the LAYER and install it again on a new LAYER created. This method can keep the software useful, but quite troublesome.
Sorry, I forget where I download it from. I can just put the file I has downloaded to Rapidshare. You may download and try it:

http://rapidshare.com/files/42990825/Software_Virtualization_Agent.msi

3. There are a lot.
eg:你必須去安裝解rar的軟體
windows的解壓縮軟體並不能解rar的
解完rar後，再解一次zip就可以了
推薦免費軟體
軟體名稱：7-Zip
軟體版本：4.33 Alpha 2
授權類型：免費軟體
支援語系：多國語言(包含繁體中文)
官方網站：http://www.7-zip.org /
檔案下載：http://www.7-zip.org /alpha/7z433a2.exe
軟體簡介：
擁有自創的高壓縮比率檔案格式 7z format
支援格式(壓縮/解壓縮)：7z、ZIP、GZIP、BZIP2、TAR
支援格式(解壓縮)：RAR、CAB、ARJ、LZH、CHM、Z、CPIO、RPM、DEB
7-Zip的壓縮率比WinZip和*****Zip高2-10%
可以製作7z檔案格式的自動解壓縮檔
支援超過60種語言

-----from:
http://hk.knowledge.yahoo.com/question/?qid=7006112500066

But if you want to create RAR, I only know WinRAR. Others I don't know. Can't help you, sorry.