0x00000077 Error on the corporate server

I'm going to make an assumption and guess that you're running Windows Server 2003. I'll appropriately retag your question as such.

Since you are unsure of what the cause of the error is, that's what we need to find out. This is my suggestion: Run chkdisk on the drive, and run memtest86+ if possible (as in, you have a few hours you can schedule for downtime)

When you say this is the corporate server, what exactly does it run? It is just a file server, or does it also host Active Directory, DHCP, DNS, DFS, anything like that? Are there any other applications that are absolutely reliant on this server? If so, you might want to consider a few things. First is getting that server out of where it is, and putting it somewhere that is 1.) climate controlled (aka in a room with a dedicated air conditioner), and 2.) secure from other employees. This will prevent a few things. First, it will make sure that no one that is unauthorized to touch it can do so. Second, it will greatly increase the life of the hardware by ensuring that it stays at appropriate temperatures. Remember, computers make heat, and that heat needs to go somewhere. If it's in a closet, that is going to get very very warm in there, and warm temperatures for computers are a Bad Thing. If you want an idea of how bad it is to have a server in rooms without air conditioning, read this article, and weep.

Also, I'm going to agree with KWPINC. Not having a backup is asking for something bad to happen. Tell your boss you need backup. If he says it's not necessary, compare the cost of a backup service (whether it is done in-house and carried offsite, or done by a managed service) to the approximate $2000 minimum for DriveSavers crack open one of your drives, and not even be able to guarantee that everything will come back.

Also, if you could, can you give us a description of the hardware your "corporate server" is running? Software would be nice as well.

Ok, based on what you've told me, I'm going to make some suggestions.

First: Get RAID in there ASAP. At least RAID 1 so if a disk fails (which seems likely given your current setup) you aren't up shit's creek. And believe me, if your disk fails, and you don't have a backup, you ARE going to be up shit's creek. Many Dell systems support RAID (I have two machines in my office that have it, a Precision 380 and an Optiplex 755), so other than being cheap as hell, there's no real excuse for not doing so.

Second: Work on getting a PowerEdge or comparable server in the building, and getting things migrated over to that. You do this one of two ways. First thing you could do is just image the old server to the new one, but this is unlikely to work because of drivers and such. The proper way to bring it up would be (and this is very much so simplified) to buy the new server, join it to the domain, set it up as a BDC, mirror the file-shares over, eventually set deny permissions on the old server for file shares, then promote the new server to PDC. I'm not sure about IIS or Exchange as I don't deal with them as much as I would like to.

You might have a driver error, a heat error or a failed component (motherboard, power supply, memory, hard drive). It's impossible to tell from the information we see here.

You really ought to bring in some outside help. It may be necessary for this problem and will be necessary to properly backup your data. Once you get through this problem, an IT consultant will likely be able to improve what you're doing in half a day. You boss really needs to compare this to the cost of losing all the company's data.

Also, once this problem is fixed, take that machine out of the closet and stick it under someone's desk. Sure, that's a bad idea from a security perspective, but a good idea from a "stuff not overheating and breaking" perspective.

Looks like lots of advice so far an few answers so:

Is this going to haunt my nights or can I fix it? If yes, how?

No this will be an albatross around your neck for the simple reason that you have no backups. Even if you didn't have the error you should have an email (printed out) on hand for when it does die and something vital is lost. Then you can point to it and say "see- I asked for backups and was told we couldn't afford them/ don't need them"

Is this urgent enough for me to tell my boss to buy whatever I need to ensure the system is backed up efficiently ASAP?

If the $100 or so for a 1TB HD in order to do backups in case of a failure wasn't important before I'd venture a guess to say it won;t be important now. I'd ask but I wouldn't hold out much hope from your description

Is the Hard Drive going to die soon, and if so, will I have to cope with it like the death of my beloved cat?

Everything dies eventually. this is a likely indicator but it's impossible to tell from your description whether its the hard drive, the controller or something else.

Would it be possible that it is caused by write errors on the disk?

Maybe, but it's possible its a read error- and inpage error means that it couldn't read back a page from the disk, It's probably unlikely that it wrote the page out badly but read it ok.