What should i do to reveal/show the partition where i installed the Ubuntu?
 

I'm recently installed my pc with a copy of Ubuntu 12.04 LTS.
When i install it, i'm using the second partition of my HDD,
1 st partition 85GB with Windows Xp Professional installed there.
2 nd partition 155GB with the ubuntu,

#1
The problem is, i can't open/show the 2nd hard drive partition where i installed the ubuntu. Only the 1st partition which i installed Windows XP Professional Shows up at the taskbar. Does anyone know how to show the 2nd partition?

#2
This morning(in Indonesia time), i'm trying to connect my laptop HDD to get some data from there. On 1st boot, i tried to open it via Windows Xp. It was a success, but after that, i installed some programs and it requires a restart. After i restart, the windows asked me to do a CHKDSK, there was 30errors found on the laptop HDD, the CHKDSK fixed it. But, when it entered Windows XP(finished loading), it gave me an error message on a blue screen similar to the BSOD, "the /windows/system32/ is corrupt". And the windows restarted it self. ending in the same blue screen again and again.
Did anyone knew a way to fix the windows via ubuntu? Or a way to let me play windows games?

My PC spec:
Acer Aspire E500
Pentium IV @3.20GHz
Ram 2GB DDR2 V-Gen
ASUS Nvidia GeForce EN8500GT Silent Magic 512MB
Seagate Baracuda 250GB (dont know how many RPM this HDD got) Have 2 partitions 1st Windows XP Professional, 2nd Ubuntu 12.04 LTS "Precise Pangolin"
Seagate Momentus 500GB @5400rpm (have 2 partitions: 1st Windows, 2nd Data)

I think your two questions are separate things. Correct me if I've misunderstood.

#1 - your Ubuntu partition is probably formatted with ext4 (or ext3). Windows cannot read this - at least not with special drivers which I have no experience of. You can't install linux on an ntfs partition as it does not support the right file permissions. A good approach is to store your shared files on a third partition, formatted with ntfs.

If you really want to read the ubuntu partition from windows, look at Ext2Read | Free System Administration software downloads at SourceForge.net or chrysocome.net - Explore2fs or Ext2Fsd Project - but be careful.

#2 - can you fix a Windows installation from your ubuntu system?

Well you can certainly replace individual files and fix individual errors, but you can't run chkdsk, and of course you don't have the windows source to check what files should be where and to get the correct files. Much better to fix windows using a windows installation disk.