Questions for beginners?

Questions for beginners? -- Linux general technology-Linux technology and application information. For details, refer to the following section. I am a linux enthusiast and a newbie who has just joined the linux camp. Please kindly advise ......
I'm tired of windows. Now I use linux. I installed ubuntu with wubi a while ago. It feels pretty good. Therefore, I made up my mind to divide some partitions on the hard disk to install ubuntu. Because no disk is installed, we downloaded the ubuntu 8.04 image and installed ubuntu on the hard disk. After reading some tutorials on the internet, I tried to restart it n times (because I installed ubuntu for the first time. And some tutorials on the Internet won't work.) (my poor hard disk ......), Finally installed ubuntu. In retrospect, the installation is actually quite simple ...... Haha ......
Now I am using a dual-system (XP + ubuntu 8.04). I am using ubuntu most of the time and occasionally use windows. After all, some things can only be done in windows.
After talking about this, I have a problem: One day, windows crashed, and after windows was reinstalled, how should I fix the grub boot menu .... (I have seen some tutorials on the Internet, but most of them need to be installed with a disk for restoration. I installed ubuntu 8.04 from a hard disk without a disk)